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A thought experiment is a hypothetical situation in which a
hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...
,
theory A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may ...
, or
principle A principle is a proposition or value that is a guide for behavior or evaluation. In law, it is a rule that has to be or usually is to be followed. It can be desirably followed, or it can be an inevitable consequence of something, such as the l ...
is laid out for the purpose of thinking through its consequences.


History

The ancient Greek ''deiknymi'' (), or thought experiment, "was the most ancient pattern of
mathematical proof A mathematical proof is an inferential argument for a mathematical statement, showing that the stated assumptions logically guarantee the conclusion. The argument may use other previously established statements, such as theorems; but every pr ...
", and existed before Euclidean mathematics, where the emphasis was on the conceptual, rather than on the experimental part of a thought-experiment. Johann Witt-Hansen established that
Hans Christian Ørsted Hans Christian Ørsted ( , ; often rendered Oersted in English; 14 August 17779 March 1851) was a Danish physicist and chemist who discovered that electric currents create magnetic fields, which was the first connection found between electricit ...
was the first to use the German term ' (lit. thought experiment) circa 1812. Ørsted was also the first to use the equivalent term ' in 1820. By 1883
Ernst Mach Ernst Waldfried Josef Wenzel Mach ( , ; 18 February 1838 – 19 February 1916) was a Moravian-born Austrian physicist and philosopher, who contributed to the physics of shock waves. The ratio of one's speed to that of sound is named the Mach n ...
used the term ' in a different way, to denote exclusively the conduct of a experiment that would be subsequently performed as a by his students. Physical and mental experimentation could then be contrasted: Mach asked his students to provide him with explanations whenever the results from their subsequent, real, physical experiment differed from those of their prior, imaginary experiment. The English term ''thought experiment'' was coined (as a
calque In linguistics, a calque () or loan translation is a word or phrase borrowed from another language by literal word-for-word or root-for-root translation. When used as a verb, "to calque" means to borrow a word or phrase from another language ...
) from Mach's ', and it first appeared in the 1897 English translation of one of Mach's papers. Prior to its emergence, the activity of posing hypothetical questions that employed subjunctive reasoning had existed for a very long time (for both scientists and philosophers). The
irrealis moods In linguistics, irrealis moods (abbreviated ) are the main set of grammatical moods that indicate that a certain situation or action is not known to have happened at the moment the speaker is talking. This contrasts with the realis moods. Every ...
are ways to categorize it or to speak about it. This helps explain the extremely wide and diverse range of the application of the term "thought experiment" once it had been introduced into English. Perhaps the key experiment in the history of modern science is
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
's demonstration that falling objects must fall at the same rate regardless of their masses. This is widely thought to have been a straightforward physical demonstration, involving climbing up the Leaning Tower of Pisa and dropping two heavyweights off it, whereas in fact, it was a logical demonstration, using the 'thought experiment' technique. The 'experiment' is described by Galileo in '' Discorsi e dimostrazioni matematiche'' (1638) (literally, 'Mathematical Discourses and Demonstrations') thus: Although the extract does not convey the elegance and power of the 'demonstration' terribly well, it is clear that it is a 'thought' experiment, rather than a practical one. Strange then, as Cohen says, that philosophers and scientists alike refuse to acknowledge either Galileo in particular or the thought experiment technique in general for its pivotal role in both science and philosophy. (The exception proves the rule – the iconoclastic philosopher of science, Paul Feyerabend, has also observed this methodological prejudice.) Instead, many philosophers prefer to consider 'Thought Experiments' to be merely the use of a hypothetical scenario to help understand the way things are.


Uses

The common goal of a thought experiment is to explore the potential consequences of the principle in question: Given the structure of the experiment, it may not be possible to perform it, and even if it could be performed, there need not be an intention to perform it. Examples of thought experiments include Schrödinger's cat, illustrating quantum indeterminacy through the manipulation of a perfectly sealed environment and a tiny bit of
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
substance, and Maxwell's demon, which attempts to demonstrate the ability of a hypothetical finite being to violate the
2nd law of thermodynamics The second law of thermodynamics is a physical law based on universal experience concerning heat and energy interconversions. One simple statement of the law is that heat always moves from hotter objects to colder objects (or "downhill"), unles ...
. It is a common element of
science-fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...
stories. Thought experiments, which are well-structured, well-defined hypothetical questions that employ
subjunctive The subjunctive (also known as conjunctive in some languages) is a grammatical mood, a feature of the utterance that indicates the speaker's attitude towards it. Subjunctive forms of verbs are typically used to express various states of unreality s ...
reasoning (
irrealis moods In linguistics, irrealis moods (abbreviated ) are the main set of grammatical moods that indicate that a certain situation or action is not known to have happened at the moment the speaker is talking. This contrasts with the realis moods. Every ...
) – "What might happen (or, what might have happened) if . . . " – have been used to pose questions in philosophy at least since Greek antiquity, some pre-dating
Socrates Socrates (; ; –399 BC) was a Greek philosopher from Athens who is credited as the founder of Western philosophy and among the first moral philosophers of the ethical tradition of thought. An enigmatic figure, Socrates authored no t ...
. In physics and other sciences many thought experiments date from the 19th and especially the 20th Century, but examples can be found at least as early as
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
. In thought experiments, we gain new information by rearranging or reorganizing already known empirical data in a new way and drawing new (a priori) inferences from them or by looking at these data from a different and unusual perspective. In Galileo's thought experiment, for example, the rearrangement of empirical experience consists of the original idea of combining bodies of different weights. Thought experiments have been used in philosophy (especially ethics),
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
, and other fields (such as
cognitive psychology Cognitive psychology is the scientific study of mental processes such as attention, language use, memory, perception, problem solving, creativity, and reasoning. Cognitive psychology originated in the 1960s in a break from behaviorism, which ...
, history,
political science Political science is the scientific study of politics. It is a social science dealing with systems of governance and power, and the analysis of political activities, political thought, political behavior, and associated constitutions and ...
, economics,
social psychology Social psychology is the scientific study of how thoughts, feelings, and behaviors are influenced by the real or imagined presence of other people or by social norms. Social psychologists typically explain human behavior as a result of the ...
, law, organizational studies, marketing, and
epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evi ...
). In law, the synonym "hypothetical" is frequently used for such experiments. Regardless of their intended goal, all thought experiments display a patterned way of thinking that is designed to allow us to explain, predict and control events in a better and more productive way.


Theoretical consequences

In terms of their theoretical consequences, thought experiments generally: * challenge (or even refute) a prevailing theory, often involving the device known as reductio ad absurdum, (as in Galileo's original argument, a
proof by contradiction In logic and mathematics, proof by contradiction is a form of proof that establishes the truth or the validity of a proposition, by showing that assuming the proposition to be false leads to a contradiction. Proof by contradiction is also known ...
), * confirm a prevailing theory, * establish a new theory, or * simultaneously refute a prevailing theory and establish a new theory through a process of mutual exclusion


Practical applications

Thought experiments can produce some very important and different outlooks on previously unknown or unaccepted theories. However, they may make those theories themselves irrelevant, and could possibly create new problems that are just as difficult, or possibly more difficult to resolve. In terms of their practical application, thought experiments are generally created to: * challenge the prevailing status quo (which includes activities such as correcting
misinformation Misinformation is incorrect or misleading information. It differs from disinformation, which is ''deliberately'' deceptive. Rumors are information not attributed to any particular source, and so are unreliable and often unverified, but can turn ...
(or misapprehension), identify flaws in the argument(s) presented, to preserve (for the long-term) objectively established fact, and to refute specific assertions that some particular thing is permissible, forbidden, known, believed, possible, or necessary); *
extrapolate In mathematics, extrapolation is a type of estimation, beyond the original observation range, of the value of a variable on the basis of its relationship with another variable. It is similar to interpolation, which produces estimates between kn ...
beyond (or interpolate within) the boundaries of already established fact; * predict and forecast the (otherwise) indefinite and unknowable future; * explain the past; * the retrodiction, postdiction and hindcasting of the (otherwise) indefinite and unknowable past; * facilitate decision making, choice, and strategy selection; * solve problems, and generate ideas; * move current (often insoluble) problems into another, more helpful, and more productive problem space (e.g.:
functional fixedness Functional fixedness is a cognitive bias that limits a person to use an object only in the way it is traditionally used. The concept of functional fixedness originated in Gestalt psychology, a movement in psychology that emphasizes holistic proce ...
); * attribute causation, preventability, blame, and responsibility for specific outcomes; * assess
culpability In criminal law, culpability, or being culpable, is a measure of the degree to which an agent, such as a person, can be held morally or legally responsible for action and inaction. It has been noted that the word, culpability, "ordinarily ha ...
and
compensatory damages At common law, damages are a remedy in the form of a monetary award to be paid to a claimant as compensation for loss or injury. To warrant the award, the claimant must show that a breach of duty has caused foreseeable loss. To be recognised at ...
in social and legal contexts; * ensure the repeat of past success; or * examine the extent to which past events might have occurred differently. * ensure the (future) avoidance of past failures


Types

Generally speaking, there are seven types of thought experiments in which one reasons from causes to effects, or effects to causes:


Prefactual

''Prefactual (before the fact) thought experiments'' – the term prefactual was coined by Lawrence J. Sanna in 1998 — speculate on possible future outcomes, given the present, and ask "What will be the outcome if event E occurs?"


Counterfactual

''Counterfactual (contrary to established fact) thought experiments'' – the term '' counterfactual'' was coined by
Nelson Goodman Henry Nelson Goodman (7 August 1906 – 25 November 1998) was an American philosopher, known for his work on counterfactuals, mereology, the problem of induction, irrealism, and aesthetics. Life and career Goodman was born in Somerville, Ma ...
in 1947,Goodman, N., "The Problem of Counterfactual Conditionals", ''The Journal of Philosophy'', Vol.44, No.5, (27 February 1947), pp.113-128. extending
Roderick Chisholm Roderick Milton Chisholm (; November 27, 1916 – January 19, 1999) was an American philosopher known for his work on epistemology, metaphysics, free will, value theory, and the philosophy of perception. The '' Stanford Encyclopedia of Phi ...
's (1946) notion of a "contrary-to-fact conditional" – speculate on the possible outcomes of a different past; and ask "What might have happened if A had happened instead of B?" (e.g., "If
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, Theology, theologian, and author (described in his time as a "natural philosophy, natural philosopher"), widely ...
and Gottfried Leibniz ''had'' cooperated with each other, what would mathematics look like today?"). The study of counterfactual speculation has increasingly engaged the interest of scholars in a wide range of domains such as philosophy, psychology, cognitive psychology, history, political science, economics, social psychology, law, organizational theory, marketing, and epidemiology.


Semifactual

''Semifactual thought experiments'' – the term ''semifactual'' was coined by
Nelson Goodman Henry Nelson Goodman (7 August 1906 – 25 November 1998) was an American philosopher, known for his work on counterfactuals, mereology, the problem of induction, irrealism, and aesthetics. Life and career Goodman was born in Somerville, Ma ...
in 1947 – speculate on the extent to which things might have remained the same, despite there being a different past; and asks the question Even though X happened instead of E, would Y have still occurred? (e.g., Even if the goalie ''had'' moved left, rather than right, could he have intercepted a ball that was traveling at such a speed?). Semifactual speculations are an important part of clinical medicine.


Predictive

The activity of prediction attempts to project the circumstances of the present into the future. According to David Sarewitz and Roger Pielke (1999, p123), scientific prediction takes two forms: # "The elucidation of invariant — and therefore predictive — principles of nature"; and # "
sing Singing is the act of creating musical sounds with the voice. A person who sings is called a singer, artist or vocalist (in jazz and/or popular music). Singers perform music (arias, recitatives, songs, etc.) that can be sung with or without ...
suites of observational data and sophisticated numerical models in an effort to foretell the behavior or evolution of complex phenomena". Although they perform different social and scientific functions, the only difference between the qualitatively identical activities of ''predicting'', ''forecasting,'' and ''nowcasting'' is the distance of the speculated future from the present moment occupied by the user. Whilst the activity of nowcasting, defined as "a detailed description of the current weather along with forecasts obtained by extrapolation up to 2 hours ahead", is essentially concerned with describing the current state of affairs, it is common practice to extend the term "to cover very-short-range forecasting up to 12 hours ahead" (Browning, 1982, p.ix).


Hindcasting

The activity of hindcasting involves running a forecast model after an event has happened in order to test whether the model's
simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or proc ...
is valid.


Retrodiction

The activity of '' retrodiction'' (or ''postdiction'') involves moving backward in time, step-by-step, in as many stages as are considered necessary, from the present into the speculated past to establish the ultimate cause of a specific event (e.g., reverse engineering and
forensics Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and crimin ...
). Given that retrodiction is a process in which "past observations, events, add and data are used as evidence to infer the process(es) that produced them" and that
diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine "cause and effect". In systems engin ...
"involve going from visible effects such as symptoms, signs and the like to their prior causes", the essential balance between prediction and retrodiction could be characterized as: regardless of whether the
prognosis Prognosis ( Greek: πρόγνωσις "fore-knowing, foreseeing") is a medical term for predicting the likely or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) or remain sta ...
is of the course of the disease in the absence of treatment, or of the application of a specific treatment regimen to a specific disorder in a particular patient.


Backcasting

The activity of '' backcasting'' – the term ''backcasting'' was coined by John Robinson in 1982 — involves establishing the description of a very definite and very specific future situation. It then involves an imaginary moving backward in time, step-by-step, in as many stages as are considered necessary, from the future to the present to reveal the mechanism through which that particular specified future could be attained from the present. Backcasting is not concerned with predicting the future: According to Jansen (1994, p. 503:


Fields

Thought experiments have been used in a variety of fields, including philosophy, law,
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...
, and mathematics. In philosophy they have been used at least since
classical antiquity Classical antiquity (also the classical era, classical period or classical age) is the period of cultural history between the 8th century BC and the 5th century AD centred on the Mediterranean Sea, comprising the interlocking civilizations of ...
, some pre-dating
Socrates Socrates (; ; –399 BC) was a Greek philosopher from Athens who is credited as the founder of Western philosophy and among the first moral philosophers of the ethical tradition of thought. An enigmatic figure, Socrates authored no t ...
. In law, they were well known to
Roman law Roman law is the legal system of ancient Rome, including the legal developments spanning over a thousand years of jurisprudence, from the Twelve Tables (c. 449 BC), to the '' Corpus Juris Civilis'' (AD 529) ordered by Eastern Roman emperor J ...
yers quoted in the
Digest Digest may refer to: Biology *Digestion of food *Restriction digest Literature and publications *'' The Digest'', formerly the English and Empire Digest *Digest size magazine format * ''Digest'' (Roman law), also known as ''Pandects'', a digest ...
. In physics and other sciences, notable thought experiments date from the 19th and especially the 20th century, but examples can be found at least as early as
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
.


Philosophy

In philosophy, a thought experiment typically presents an imagined scenario with the intention of eliciting an intuitive or reasoned response about the way things are in the thought experiment. (Philosophers might also supplement their thought experiments with theoretical reasoning designed to support the desired intuitive response.) The scenario will typically be designed to target a particular philosophical notion, such as morality, or the nature of the mind or linguistic reference. The response to the imagined scenario is supposed to tell us about the nature of that notion in any scenario, real or imagined. For example, a thought experiment might present a situation in which an agent intentionally kills an innocent for the benefit of others. Here, the relevant question is not whether the action is moral or not, but more broadly whether a moral theory is correct that says morality is determined solely by an action's consequences (See Consequentialism).
John Searle John Rogers Searle (; born July 31, 1932) is an American philosopher widely noted for contributions to the philosophy of language, philosophy of mind, and social philosophy. He began teaching at UC Berkeley in 1959, and was Willis S. and Mari ...
imagines a man in a locked room who receives written sentences in Chinese, and returns written sentences in Chinese, according to a sophisticated instruction manual. Here, the relevant question is not whether or not the man understands Chinese, but more broadly, whether a functionalist theory of mind is correct. It is generally hoped that there is universal agreement about the intuitions that a thought experiment elicits. (Hence, in assessing their own thought experiments, philosophers may appeal to "what we should say," or some such locution.) A successful thought experiment will be one in which intuitions about it are widely shared. But often, philosophers differ in their intuitions about the scenario. Other philosophical uses of imagined scenarios arguably are thought experiments also. In one use of scenarios, philosophers might imagine persons in a particular situation (maybe ourselves), and ask what they would do. For example, in the veil of ignorance, John Rawls asks us to imagine a group of persons in a situation where they know nothing about themselves, and are charged with devising a social or political organization. The use of the state of nature to imagine the origins of government, as by
Thomas Hobbes Thomas Hobbes ( ; 5/15 April 1588 – 4/14 December 1679) was an English philosopher, considered to be one of the founders of modern political philosophy. Hobbes is best known for his 1651 book '' Leviathan'', in which he expounds an influ ...
and
John Locke John Locke (; 29 August 1632 – 28 October 1704) was an English philosopher and physician, widely regarded as one of the most influential of Enlightenment thinkers and commonly known as the "father of liberalism". Considered one of ...
, may also be considered a thought experiment.
Søren Kierkegaard Søren Aabye Kierkegaard ( , , ; 5 May 1813 – 11 November 1855) was a Danish theologian, philosopher, poet, social critic, and religious author who is widely considered to be the first existentialist philosopher. He wrote critical texts on ...
explored the possible ethical and religious implications of
Abraham Abraham, ; ar, , , name=, group= (originally Abram) is the common Hebrew patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father of the special relationship between the Je ...
's
binding of Isaac The Binding of Isaac ( he, , ), or simply "The Binding" (, ), is a story from Genesis 22 of the Hebrew Bible. In the biblical narrative, God tells Abraham to sacrifice his son, Isaac, on Moriah. As Abraham begins to comply, having bound Isa ...
in '' Fear and Trembling''. Similarly,
Friedrich Nietzsche Friedrich Wilhelm Nietzsche (; or ; 15 October 1844 – 25 August 1900) was a German philosopher, prose poet, cultural critic, philologist, and composer whose work has exerted a profound influence on contemporary philosophy. He began his ...
, in '' On the Genealogy of Morals'', speculated about the historical development of Judeo-Christian morality, with the intent of questioning its legitimacy. An early written thought experiment was
Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...
's allegory of the cave. Another historic thought experiment was
Avicenna Ibn Sina ( fa, ابن سینا; 980 – June 1037 CE), commonly known in the West as Avicenna (), was a Persian polymath who is regarded as one of the most significant physicians, astronomers, philosophers, and writers of the Islamic ...
's " Floating Man" thought experiment in the 11th century. He asked his readers to imagine themselves suspended in the air isolated from all sensations in order to demonstrate human
self-awareness In philosophy of self, self-awareness is the experience of one's own personality or individuality. It is not to be confused with consciousness in the sense of qualia. While consciousness is being aware of one's environment and body and lifest ...
and self-consciousness, and the substantiality of the
soul In many religious and philosophical traditions, there is a belief that a soul is "the immaterial aspect or essence of a human being". Etymology The Modern English noun '' soul'' is derived from Old English ''sāwol, sāwel''. The earliest att ...
.


Science

Scientists tend to use thought experiments as imaginary, "proxy" experiments prior to a real, "physical" experiment (
Ernst Mach Ernst Waldfried Josef Wenzel Mach ( , ; 18 February 1838 – 19 February 1916) was a Moravian-born Austrian physicist and philosopher, who contributed to the physics of shock waves. The ratio of one's speed to that of sound is named the Mach n ...
always argued that these ''gedankenexperiments'' were "a necessary precondition for physical experiment"). In these cases, the result of the "proxy" experiment will often be so clear that there will be no need to conduct a physical experiment at all. Scientists also use thought experiments when particular physical experiments are impossible to conduct (
Carl Gustav Hempel Carl Gustav "Peter" Hempel (January 8, 1905 – November 9, 1997) was a German writer, philosopher, logician, and epistemologist. He was a major figure in logical empiricism, a 20th-century movement in the philosophy of science. He is e ...
labeled these sorts of experiment "''theoretical experiments-in-imagination''"), such as Einstein's thought experiment of chasing a light beam, leading to
special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The law ...
. This is a unique use of a scientific thought experiment, in that it was never carried out, but led to a successful theory, proven by other empirical means.


Properties

Further categorization of thought experiments can be attributed to specific properties.


Possibility

In many thought experiments, the scenario would be nomologically possible, or possible according to the laws of nature. John Searle's
Chinese room The Chinese room argument holds that a digital computer executing a program cannot have a " mind," "understanding" or "consciousness," regardless of how intelligently or human-like the program may make the computer behave. The argument was pres ...
is nomologically possible. Some thought experiments present scenarios that are not nomologically possible. In his
Twin Earth thought experiment Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of 'Meaning (1975). It is meant to serve as an illustration of his argument for semantic externalism, or the ...
, Hilary Putnam asks us to imagine a scenario in which there is a substance with all of the observable properties of water (e.g., taste, color, boiling point), but is chemically different from water. It has been argued that this thought experiment is not nomologically possible, although it may be possible in some other sense, such as metaphysical possibility. It is debatable whether the nomological impossibility of a thought experiment renders intuitions about it moot. In some cases, the hypothetical scenario might be considered metaphysically impossible, or impossible in any sense at all. David Chalmers says that we can imagine that there are zombies, or persons who are physically identical to us in every way but who lack consciousness. This is supposed to show that
physicalism In philosophy, physicalism is the metaphysical thesis that "everything is physical", that there is "nothing over and above" the physical, or that everything supervenes on the physical. Physicalism is a form of ontological monism—a "one substanc ...
is false. However, some argue that zombies are inconceivable: we can no more imagine a zombie than we can imagine that 1+1=3. Others have claimed that the conceivability of a scenario may not entail its possibility.


Causal reasoning

The first characteristic pattern that thought experiments display is their orientation in time. They are either: *''Antefactual speculations'': experiments that speculate about what might have happened prior to a specific, designated event, or *''Postfactual speculations'': experiments that speculate about what may happen subsequent to (or consequent upon) a specific, designated event. The second characteristic pattern is their movement in time in relation to "the present moment standpoint" of the individual performing the experiment; namely, in terms of: * Their ''temporal direction'': are they past-oriented or future-oriented? * Their ''temporal sense'': **(a) in the case of past-oriented thought experiments, are they examining the consequences of temporal "movement" from the present to the past, or from the past to the present? or, **(b) in the case of future-oriented thought experiments, are they examining the consequences of temporal "movement" from the present to the future, or from the future to the present?


Relation to real experiments

The relation to real experiments can be quite complex, as can be seen again from an example going back to Albert Einstein. In 1935, with two coworkers, he published a paper on a newly created subject called later the EPR effect (
EPR paradox EPR may refer to: Science and technology * EPR (nuclear reactor), European Pressurised-Water Reactor * EPR paradox (Einstein–Podolsky–Rosen paradox), in physics * Earth potential rise, in electrical engineering * East Pacific Rise, a mid-oce ...
). In this paper, starting from certain philosophical assumptions, on the basis of a rigorous analysis of a certain, complicated, but in the meantime assertedly realizable model, he came to the conclusion that ''quantum mechanics should be described as "incomplete"''. Niels Bohr asserted a refutation of Einstein's analysis immediately, and his view prevailed. After some decades, it was asserted that feasible experiments could prove the error of the EPR paper. These experiments tested the Bell inequalities published in 1964 in a purely theoretical paper. The above-mentioned EPR philosophical starting assumptions were considered to be falsified by the empirical fact (e.g. by the optical ''real experiments'' of Alain Aspect). Thus ''thought experiments'' belong to a theoretical discipline, usually to
theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experim ...
, but often to theoretical philosophy. In any case, it must be distinguished from a real experiment, which belongs naturally to the experimental discipline and has "the final decision on ''true'' or ''not true''", at least in physics.


Interactivity

Thought experiments can also be interactive where the author invites people into his thought process through providing alternative paths with alternative outcomes within the narrative, or through interaction with a programmed machine, like a computer program. Thanks to the advent of the Internet, the digital space has lent itself as a new medium for a new kind of thought experiments. The philosophical work of Stefano Gualeni, for example, focuses on the use of virtual worlds to materialize thought experiments and to playfully negotiate philosophical ideas. His arguments were originally presented in his book ''Virtual Worlds as Philosophical Tools''. Gualeni's argument is that the history of philosophy has, until recently, merely been the history of written thought, and digital media can complement and enrich the limited and almost exclusively linguistic approach to philosophical thought. He considers virtual worlds to be philosophically viable and advantageous in contexts like those of thought experiments, when the recipients of a certain philosophical notion or perspective are expected to objectively test and evaluate different possible courses of action, or in cases where they are confronted with interrogatives concerning non-actual or non-human phenomenologies.


Examples


Humanities

*
Doomsday argument The Doomsday Argument (DA), or Carter catastrophe, is a probabilistic argument that claims to predict the future population of the human species, based on an estimation of the number of humans born to date. The Doomsday argument was originally ...
( anthropic principle) * The Lady, or the Tiger? (human nature)While the problem presented in this short story's scenario is not unique, it is extremely unusual. Most thought experiments are intentionally (or, even, sometimes unintentionally) skewed towards the inevitable production of a particular solution to the problem posed; and this happens because of the way that the problem and the scenario are framed in the first place. In the case of ''The Lady, or the Tiger?'', the way that the story unfolds is so "end-neutral" that, at the finish, there is no "correct" solution to the problem. Therefore, all that one can do is to offer one's own innermost thoughts on how the account of human nature that has been presented might unfold – according to one's own experience of human nature – which is, obviously, the purpose of the entire exercise. The extent to which the story can provoke such an extremely wide range of (otherwise equipollent) predictions of the participants' subsequent behaviour is one of the reasons the story has been so popular over time. * The beer question (
U.S. politics The politics of the United States function within a framework of a constitutional federal republic and presidential system, with three distinct branches that share powers. These are: the U.S. Congress which forms the legislative branch, a bic ...
)


Physics

* Bell's spaceship paradox (
special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The law ...
) * Brownian ratchet ( Richard Feynman's "
perpetual motion Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, a ...
" machine that does not violate the second law and does no work at thermal equilibrium) * Bucket argument – argues that space is absolute, not relational * Dyson sphere * Einstein's box * Elitzur–Vaidman bomb-tester (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) *
EPR paradox EPR may refer to: Science and technology * EPR (nuclear reactor), European Pressurised-Water Reactor * EPR paradox (Einstein–Podolsky–Rosen paradox), in physics * Earth potential rise, in electrical engineering * East Pacific Rise, a mid-oce ...
(
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) (forms of this have been performed) * Feynman sprinkler (classical mechanics) * Galileo's Leaning Tower of Pisa experiment (rebuttal of Aristotelian Gravity) *
Galileo's ship Galileo's ship refers to two physics experiments, a thought experiment and an actual experiment, by Galileo Galilei, the 16th and 17th century physicist and astronomer. The experiments were created to argue the idea of a rotating Earth as oppose ...
(classical relativity principle) 1632 *
GHZ experiment The Greenberger–Horne–Zeilinger experiment or GHZ experiments are a class of physics experiments that may be used to generate starkly contrasting predictions from local hidden-variable theory and quantum mechanical theory, and permit immediate ...
(
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Heisenberg's microscope (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Kepler's Dream (change of point of view as support for the Copernican hypothesis) * Ladder paradox (
special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The law ...
) * Laplace's demon * Maxwell's demon (
thermodynamics Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws ...
) 1871 * Moving magnet and conductor problem *
Newton's cannonball Newton's cannonball was a thought experiment Isaac Newton used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion. It appeared in his posthumously published 1728 work ''De mundi systemate'' (also ...
(
Newton's laws of motion Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in mo ...
) * Popper's experiment (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Quantum pseudo telepathy (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Quantum suicide and immortality (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Renninger negative-result experiment (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Schrödinger's cat (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Sticky bead argument (
general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...
) * The Monkey and the Hunter (
gravitation In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
) *
Twin paradox In physics, the twin paradox is a thought experiment in special relativity involving identical twins, one of whom makes a journey into space in a high-speed rocket and returns home to find that the twin who remained on Earth has aged more. T ...
(
special relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The law ...
) * Wheeler's delayed choice experiment (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
) * Wigner's friend (
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
)


Philosophy

*
Artificial brain An artificial brain (or artificial mind) is software and hardware with cognitive abilities similar to those of the animal or human brain. Research investigating "artificial brains" and brain emulation plays three important roles in science: #An o ...
*
Avicenna Ibn Sina ( fa, ابن سینا; 980 – June 1037 CE), commonly known in the West as Avicenna (), was a Persian polymath who is regarded as one of the most significant physicians, astronomers, philosophers, and writers of the Islamic ...
's Floating Man * Beetle in a box * ''
Bellum omnium contra omnes ', a Latin phrase meaning "the war of all against all", is the description that Thomas Hobbes gives to human existence in the state-of-nature thought experiment that he conducts in ''De Cive'' (1642) and '' Leviathan'' (1651). The common modern ...
'' * Big Book (ethics) * Brain-in-a-vat (
epistemology Epistemology (; ), or the theory of knowledge, is the branch of philosophy concerned with knowledge. Epistemology is considered a major subfield of philosophy, along with other major subfields such as ethics, logic, and metaphysics. Epi ...
,
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
) * Brainstorm machine *
Buridan's ass Buridan's ass is an illustration of a paradox in philosophy in the conception of free will. It refers to a hypothetical situation wherein an ass (donkey) that is equally hungry and thirsty is placed precisely midway between a stack of hay and a ...
* Changing places ( reflexive monism,
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
) *
China brain In the philosophy of mind, the China brain thought experiment (also known as the Chinese Nation or Chinese Gym) considers what would happen if each member of the Chinese nation were asked to simulate the action of one neuron in the brain, using ...
(
physicalism In philosophy, physicalism is the metaphysical thesis that "everything is physical", that there is "nothing over and above" the physical, or that everything supervenes on the physical. Physicalism is a form of ontological monism—a "one substanc ...
,
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
) *
Chinese room The Chinese room argument holds that a digital computer executing a program cannot have a " mind," "understanding" or "consciousness," regardless of how intelligently or human-like the program may make the computer behave. The argument was pres ...
(
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
,
artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech ...
, cognitive science) * Coherence (philosophical gambling strategy) * Condillac's Statue (
epistemology Epistemology (; ), or the theory of knowledge, is the branch of philosophy concerned with knowledge. Epistemology is considered a major subfield of philosophy, along with other major subfields such as ethics, logic, and metaphysics. Epi ...
) * Experience machine (ethics) * Gettier problem (epistemology) * Ḥayy ibn Yaqẓān (epistemology) * Hilary Putnam's
Twin Earth thought experiment Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of 'Meaning (1975). It is meant to serve as an illustration of his argument for semantic externalism, or the ...
in the
philosophy of language In analytic philosophy, philosophy of language investigates the nature of language and the relations between language, language users, and the world. Investigations may include inquiry into the nature of Meaning (philosophy of language), meanin ...
and
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
* If a tree falls in a forest * Inverted spectrum * Kavka's toxin puzzle *
Mary's room The knowledge argument (also known as Mary's room or Mary the super-scientist) is a philosophical thought experiment proposed by Frank Jackson in his article "Epiphenomenal Qualia" (1982) and extended in "What Mary Didn't Know" (1986). The experim ...
(
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
) * Molyneux's Problem (admittedly, this oscillated between empirical and a-priori assessment) *
Newcomb's paradox In philosophy and mathematics, Newcomb's paradox, also known as Newcomb's problem, is a thought experiment involving a game between two players, one of whom is able to predict the future. Newcomb's paradox was created by William Newcomb of the ...
* Original position (politics) * Philosophical zombie (
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
,
artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech ...
, cognitive science) * Plank of Carneades * Roko's basilisk *
Ship of Theseus The Ship of Theseus is a thought experiment about whether an object that has had all of its original components replaced remains the same object. According to legend, Theseus, the mythical Greek founder-king of Athens, had rescued the children o ...
, The (concept of
identity Identity may refer to: * Identity document * Identity (philosophy) * Identity (social science) * Identity (mathematics) Arts and entertainment Film and television * ''Identity'' (1987 film), an Iranian film * ''Identity'' (2003 film), an ...
) * Shoemaker's "''Time Without Change''" (metaphysics) *
Simulated reality The simulation theory is the hypothesis that reality could be simulated—for example by quantum computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds that may or may not know that they live i ...
(philosophy,
computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
, cognitive science) *
Social contract In moral and political philosophy, the social contract is a theory or model that originated during the Age of Enlightenment and usually, although not always, concerns the legitimacy of the authority of the state over the individual. Social ...
theories * Survival lottery, The (ethics) * Swamp man ( personal identity,
philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind and its relationship with the body. The mind–body problem is a paradigmatic issue in philosophy of mind, although a number of other issues are add ...
) *
Teleportation Teleportation is the hypothetical transfer of matter or energy from one point to another without traversing the physical space between them. It is a common subject in science fiction literature and in other popular culture. Teleportation is oft ...
(metaphysics) * The Transparent eyeball * The Violinist (ethics) *
Ticking time bomb scenario The ticking time bomb scenario is a thought experiment that has been used in the ethics debate over whether interrogational torture can ever be justified. The scenario can be formulated as follows: Suppose that a person with knowledge of an immin ...
(ethics) * Trolley problem (ethics) *
Utility monster The utility monster is a thought experiment in the study of ethics created by philosopher Robert Nozick in 1974 as a criticism of utilitarianism. The thought experiment A hypothetical being, which Nozick calls the ''utility monster,'' receives m ...
(ethics) * Zeno's paradoxes (classical Greek problems of the infinite)


Mathematics

* Balls and vase problem (infinity and cardinality) * Gabriel's Horn (infinity) * Hilbert's paradox of the Grand Hotel (infinity) *
Infinite monkey theorem The infinite monkey theorem states that a monkey hitting keys at random on a typewriter keyboard for an infinite amount of time will almost surely type any given text, such as the complete works of William Shakespeare. In fact, the monkey would ...
(probability) * Lottery paradox (probability) * Sleeping beauty paradox (probability)


Biology

*
Levinthal paradox Levinthal's paradox is a thought experiment, also constituting a self-reference in the theory of protein folding. In 1969, Cyrus Levinthal noted that, because of the very large number of degrees of freedom in an unfolded polypeptide chain, the mol ...
* Rotating locomotion in living systems


Computer science

* Braitenberg vehicles (robotics, neural control and sensing systems) (some have been built) * Dining Philosophers (
computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
) *
Halting problem In computability theory, the halting problem is the problem of determining, from a description of an arbitrary computer program and an input, whether the program will finish running, or continue to run forever. Alan Turing proved in 1936 that a ...
(limits of computability) *
Turing machine A Turing machine is a mathematical model of computation describing an abstract machine that manipulates symbols on a strip of tape according to a table of rules. Despite the model's simplicity, it is capable of implementing any computer alg ...
(limits of computability) *
Two Generals' Problem In computing, the Two Generals' Problem is a thought experiment meant to illustrate the pitfalls and design challenges of attempting to coordinate an action by communicating over an unreliable link. In the experiment, two generals are only able ...


Economics

* Broken window fallacy ( law of unintended consequences, opportunity cost) * Laffer Curve


See also

*
Alternate history Alternate history (also alternative history, althist, AH) is a genre of speculative fiction of stories in which one or more historical events occur and are resolved differently than in real life. As conjecture based upon historical fact, alte ...
* Aporia * Black box * Brainstorm machine * '' Ding an sich'' * Einstein's thought experiments *
Futures studies Futures studies, futures research, futurism or futurology is the systematic, interdisciplinary and holistic study of social and technological advancement, and other environmental trends, often for the purpose of exploring how people will l ...
* Futures techniques *
Heuristic A heuristic (; ), or heuristic technique, is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediate ...
* Intuition pump *
Mathematical proof A mathematical proof is an inferential argument for a mathematical statement, showing that the stated assumptions logically guarantee the conclusion. The argument may use other previously established statements, such as theorems; but every pr ...
* N-universes * Possible world * Scenario planning * Scenario test *
Theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experim ...


Notes


References


Further reading


Brendal, Elke, "Intuition Pumps and the Proper Use of Thought Experiments", ''Dialectica'', Vol.58, No.1, (March 2004, pp.89–108.
* Ćorić, Dragana (2020), "The Importance of Thought Experiments", ''Journal of Eastern-European Criminal Law'', Vol.2020, No.1, (2020), pp. 127–135.
Cucic, D.A. & Nikolic, A.S., "A short insight about thought experiment in modern physics", ''6th International Conference of the Balkan Physical Union BPU6'', Istanbul – Turkey, 2006.
* Dennett, D.C., "Intuition Pumps", pp. 180–197 in Brockman, J., ''The Third Culture: Beyond the Scientific Revolution'', Simon & Schuster, (New York), 1995.
Galton, F., "Statistics of Mental Imagery", ''Mind'', Vol.5, No.19, (July 1880), pp. 301–318.
* Hempel, C.G., "Typological Methods in the Natural and Social Sciences", pp. 155–171 in Hempel, C.G. (ed.), ''Aspects of Scientific Explanation and Other Essays in the Philosophy of Science'', The Free Press, (New York), 1965. * Jacques, V., Wu, E., Grosshans, F., Treussart, F., Grangier, P. Aspect, A., & Roch, J. (2007)
Experimental Realization of Wheeler's Delayed-Choice Gedanken Experiment
''Science, 315'', p. 966–968. * Kuhn, T., "A Function for Thought Experiments", in ''The Essential Tension'' (Chicago: University of Chicago Press, 1979), pp. 240–265. * Mach, E.
"On Thought Experiments", pp. 134–147 in Mach, E., ''Knowledge and Error: Sketches on the Psychology of Enquiry'', D. Reidel Publishing Co., (Dordrecht), 1976. [Translation of ''Erkenntnis und Irrtum'' (5th edition, 1926.].
* Popper, K.
"On the Use and Misuse of Imaginary Experiments, Especially in Quantum Theory"
pp. 442–456, in Popper, K., ''The Logic of Scientific Discovery'', Harper Torchbooks, (New York), 1968. * Stuart, M. T., Fehige, Y. and Brown, J. R. (2018). The Routledge Companion to Thought Experiments. London: Routledge. * Witt-Hansen, J., "H.C. Ørsted, Immanuel Kant and the Thought Experiment", ''Danish Yearbook of Philosophy'', Vol.13, (1976), pp. 48–65.


Bibliography

* Adams, Scott, ''God's Debris: A Thought Experiment'', Andrews McMeel Publishing, (USA), 2001 * Browning, K.A. (ed.), ''Nowcasting'', Academic Press, (London), 1982. * Buzzoni, M., ''Thought Experiment in the Natural Sciences'', Koenigshausen+Neumann, Wuerzburg 2008 * Cohen, Martin, "Wittgenstein's Beetle and Other Classic Thought Experiments", Blackwell (Oxford) 2005 * Cohnitz, D., ''Gedankenexperimente in der Philosophie'', Mentis Publ., (Paderborn, Germany), 2006. * Craik, K.J.W., ''The Nature of Explanation'', Cambridge University Press, (Cambridge), 1943. * Cushing, J.T., ''Philosophical Concepts in Physics: The Historical Relation Between Philosophy and Scientific Theories'', Cambridge University Press, (Cambridge), 1998. * DePaul, M. & Ramsey, W. (eds.), ''Rethinking Intuition: The Psychology of Intuition and Its Role in Philosophical Inquiry'', Rowman & Littlefield Publishers, (Lanham), 1998. * Gendler, T.S. & Hawthorne, J., ''Conceivability and Possibility'', Oxford University Press, (Oxford), 2002. * Gendler, T.S., ''Thought Experiment: On the Powers and Limits of Imaginary Cases'', Garland, (New York), 2000. * Häggqvist, S., ''Thought Experiments in Philosophy'', Almqvist & Wiksell International, (Stockholm), 1996. * Hanson, N.R., ''Patterns of Discovery: An Inquiry into the Conceptual Foundations of Science'', Cambridge University Press, (Cambridge), 1962. * Harper, W.L., Stalnaker, R. & Pearce, G. (eds.), ''Ifs: Conditionals, Belief, Decision, Chance, and Time'', D. Reidel Publishing Co., (Dordrecht), 1981. * Hesse, M.B., ''Models and Analogies in Science'', Sheed and Ward, (London), 1963. * Holyoak, K.J. & Thagard, P., ''Mental Leaps: Analogy in Creative Thought'', A Bradford Book, The MIT Press, (Cambridge), 1995. * Horowitz, T. & Massey, G.J. (eds.)
''Thought Experiments in Science and Philosophy''
Rowman & Littlefield, (Savage), 1991. * Kahn, H., ''Thinking About the Unthinkable'', Discus Books, (New York), 1971. * Kuhne, U., ''Die Methode des Gedankenexperiments'', Suhrkamp Publ., (Frankfurt/M, Germany), 2005. * Leatherdale, W.H., ''The Role of Analogy, Model and Metaphor in Science'', North-Holland Publishing Company, (Amsterdam), 1974. * . Translated to English by Karen Jelved, Andrew D. Jackson, and Ole Knudsen, (translators 1997). * Roese, N.J. & Olson, J.M. (eds.), ''What Might Have Been: The Social Psychology of Counterfactual Thinking'', Lawrence Erlbaum Associates, (Mahwah), 1995. * Shanks, N. (ed.), ''Idealization IX: Idealization in Contemporary Physics (Poznan Studies in the Philosophy of the Sciences and the Humanities, Volume 63)'', Rodopi, (Amsterdam), 1998. * Shick, T. & Vaugn, L., ''Doing Philosophy: An Introduction through Thought Experiments (Second Edition)'', McGraw Hill, (New York), 2003. * Sorensen, R.A., ''Thought Experiments'', Oxford University Press, (Oxford), 1992. * Tetlock, P.E. & Belkin, A. (eds.), ''Counterfactual Thought Experiments in World Politics'', Princeton University Press, (Princeton), 1996. * Thomson, J.J. , ''Rights, Restitution, and Risks: Essays in Moral Theory'', Harvard University Press, (Cambridge), 1986. * Vosniadou, S. & Ortony. A. (eds.), ''Similarity and Analogical Reasoning'', Cambridge University Press, (Cambridge), 1989. * Wilkes, K.V., ''Real People: Personal Identity without Thought Experiments'', Oxford University Press, (Oxford), 1988.
Yeates, L.B., ''Thought Experimentation: A Cognitive Approach'', Graduate Diploma in Arts (By Research) Dissertation, University of New South Wales, 2004.


External links

* *

Short essay by S. Abbas Raza of ''
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Thought experiment generator
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