Epistemic Impossibility
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Epistemic Impossibility
In philosophy and modal logic, epistemic possibility relates a statement under consideration to the current state of our knowledge about the actual world: a statement is said to be: * ''epistemically possible'' if it ''may be true, for all we know'' * ''epistemically necessary'' if it is ''certain'' (or ''must be the case), given what we know'' * ''epistemically impossible'' if it ''cannot be true, given what we know'' Epistemic possibility is often contrasted with subjunctive possibility (or alethic possibility), and although epistemic and subjunctive possibilities are often expressed using the same modal terms (such as ''possibly'', ''could be'', ''must be'') or similar modal terms that are sometimes confused (such as ''may be'' and ''might be''), statements that are qualified in terms of epistemic possibility and statements that are qualified in terms of subjunctive possibility have importantly different meanings. The contrast is best explained by example. Consider the two st ...
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Philosophy
Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational and critical inquiry that reflects on its methods and assumptions. Historically, many of the individual sciences, such as physics and psychology, formed part of philosophy. However, they are considered separate academic disciplines in the modern sense of the term. Influential traditions in the history of philosophy include Western philosophy, Western, Islamic philosophy, Arabic–Persian, Indian philosophy, Indian, and Chinese philosophy. Western philosophy originated in Ancient Greece and covers a wide area of philosophical subfields. A central topic in Arabic–Persian philosophy is the relation between reason and revelation. Indian philosophy combines the Spirituality, spiritual problem of how to reach Enlightenment in Buddhism, enlighten ...
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Modal Logic
Modal logic is a kind of logic used to represent statements about Modality (natural language), necessity and possibility. In philosophy and related fields it is used as a tool for understanding concepts such as knowledge, obligation, and causality, causation. For instance, in epistemic modal logic, the well-formed_formula, formula \Box P can be used to represent the statement that P is known. In deontic modal logic, that same formula can represent that P is a moral obligation. Modal logic considers the inferences that modal statements give rise to. For instance, most epistemic modal logics treat the formula \Box P \rightarrow P as a Tautology_(logic), tautology, representing the principle that only true statements can count as knowledge. However, this formula is not a tautology in deontic modal logic, since what ought to be true can be false. Modal logics are formal systems that include unary operation, unary operators such as \Diamond and \Box, representing possibility and necessi ...
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Knowledge
Knowledge is an Declarative knowledge, awareness of facts, a Knowledge by acquaintance, familiarity with individuals and situations, or a Procedural knowledge, practical skill. Knowledge of facts, also called propositional knowledge, is often characterized as Truth, true belief that is distinct from opinion or guesswork by virtue of Justification (epistemology), justification. While there is wide agreement among philosophers that propositional knowledge is a form of true belief, many controversies focus on justification. This includes questions like how to understand justification, whether it is needed at all, and whether something else besides it is needed. These controversies intensified in the latter half of the 20th century due to a series of thought experiments called ''Gettier cases'' that provoked alternative definitions. Knowledge can be produced in many ways. The main source of empirical knowledge is perception, which involves the usage of the senses to learn about ...
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Actual World
A possible world is a complete and consistent way the world is or could have been. Possible worlds are widely used as a formal device in logic, philosophy, and linguistics in order to provide a semantics for intensional and modal logic. Their metaphysical status has been a subject of controversy in philosophy, with modal realists such as David Lewis arguing that they are literally existing alternate realities, and others such as Robert Stalnaker arguing that they are not. Logic Possible worlds are one of the foundational concepts in modal and intensional logics. Formulas in these logics are used to represent statements about what ''might'' be true, what ''should'' be true, what one ''believes'' to be true and so forth. To give these statements a formal interpretation, logicians use structures containing possible worlds. For instance, in the relational semantics for classical propositional modal logic, the formula \Diamond P (read as "possibly P") is actually true if and onl ...
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Subjunctive Possibility
Subjunctive possibility (also called alethic possibility) is a form of modality studied in modal logic. Subjunctive possibilities are the sorts of possibilities considered when conceiving counterfactual situations; subjunctive modalities are modalities that bear on whether a statement ''might have been'' or ''could be'' true—such as ''might'', ''could'', ''must'', ''possibly'', ''necessarily'', ''contingently'', ''essentially'', ''accidentally'', and so on. Subjunctive possibilities include logical possibility, metaphysical possibility, nomological possibility, and temporal possibility. Subjunctive possibility and other modalities Subjunctive possibility is contrasted with (among other things) epistemic possibility (which deals with how the world ''may'' be, ''for all we know'') and deontic possibility (which deals with how the world ''ought'' to be). Epistemic possibility The contrast with epistemic possibility is especially important to draw, since in ordinary langua ...
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Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea in the south. The Japanese archipelago consists of four major islands—Hokkaido, Honshu, Shikoku, and Kyushu—and List of islands of Japan, thousands of smaller islands, covering . Japan has a population of over 123 million as of 2025, making it the List of countries and dependencies by population, eleventh-most populous country. The capital of Japan and List of cities in Japan, its largest city is Tokyo; the Greater Tokyo Area is the List of largest cities, largest metropolitan area in the world, with more than 37 million inhabitants as of 2024. Japan is divided into 47 Prefectures of Japan, administrative prefectures and List of regions of Japan, eight traditional regions. About three-quarters of Geography of Japan, the countr ...
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World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks in World War II, Tanks and Air warfare of World War II, aircraft played major roles, enabling the strategic bombing of cities and delivery of the Atomic bombings of Hiroshima and Nagasaki, first and only nuclear weapons ever used in war. World War II is the List of wars by death toll, deadliest conflict in history, causing World War II casualties, the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Allied-occupied Germany, Germany, Allied-occupied Austria, Austria, Occupation of Japan, Japan, a ...
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Counterfactual Conditional
Counterfactual conditionals (also ''contrafactual'', ''subjunctive'' or ''X-marked'') are conditional sentences which discuss what would have been true under different circumstances, e.g. "If Peter believed in ghosts, he would be afraid to be here." Counterfactuals are contrasted with indicatives, which are generally restricted to discussing open possibilities. Counterfactuals are characterized grammatically by their use of fake tense morphology, which some languages use in combination with other kinds of morphology including aspect and mood. Counterfactuals are one of the most studied phenomena in philosophical logic, formal semantics, and philosophy of language. They were first discussed as a problem for the material conditional analysis of conditionals, which treats them all as trivially true. Starting in the 1960s, philosophers and linguists developed the now-classic possible world approach, in which a counterfactual's truth hinges on its consequent holding at certai ...
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Indicative
A realis mood ( abbreviated ) is a grammatical mood which is used principally to indicate that something is a statement of fact; in other words, to express what the speaker considers to be a known state of affairs, as in declarative sentence Declarative may refer to: * Declarative learning, acquiring information that one can speak about * Declarative memory, one of two types of long term human memory * Declarative programming In computer science, declarative programming is a programm ...s. Most languages have a single realis mood called the indicative mood, although some languages have additional realis moods, for example to express different levels of certainty. By contrast, an irrealis mood is used to express something that is not known to be the case in reality. An example of the contrast between realis and irrealis moods is seen in the English sentences "He works" and "It is necessary that he work". In the first sentence, ''works'' is a present indicative (realis) form ...
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Subjunctive
The subjunctive (also known as the conjunctive in some languages) is a grammatical mood, a feature of an utterance that indicates the speaker's attitude toward it. Subjunctive forms of verbs are typically used to express various states of unreality, such as wish, emotion, possibility, judgment, opinion, obligation, or action, that has not yet occurred. The precise situations in which they are used vary from language to language. The subjunctive is one of the irrealis moods, which refer to what is not necessarily real. It is often contrasted with the indicative, a realis mood which principally indicates that something is a statement of fact. Subjunctives occur most often, although not exclusively, in subordinate clauses, particularly ''that''-clauses. Examples of the subjunctive in English are found in the sentences "I suggest that you ''be'' careful" and "It is important that she ''stay'' by your side." Indo-European languages Proto-Indo-European The Proto-Indo-European lang ...
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Lee Harvey Oswald
Lee Harvey Oswald (October 18, 1939 – November 24, 1963) was a U.S. Marine veteran who assassinated John F. Kennedy, the 35th president of the United States, on November 22, 1963. Oswald was placed in juvenile detention at age 12 for truancy, during which he was assessed by a psychiatrist as "emotionally disturbed" due to a lack of normal family life. He attended 12 schools in his youth, quitting repeatedly, and at age 17 he joined the Marines, where he was court-martialed twice and jailed. In 1959, he was discharged from active duty into the Marine Corps Reserve, then flew to Europe and defected to the Soviet Union. He lived in Minsk, married a Russian woman named Marina, and had a daughter. In June 1962, he returned to the United States with his wife, and eventually settled in Dallas, Texas, where their second daughter was born. Oswald shot and killed Kennedy on November 22, 1963, from a sixth-floor window of the Texas School Book Depository as Kennedy traveled by moto ...
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John F
John is a common English name and surname: * John (given name) * John (surname) John may also refer to: New Testament Works * Gospel of John, a title often shortened to John * First Epistle of John, often shortened to 1 John * Second Epistle of John, often shortened to 2 John * Third Epistle of John, often shortened to 3 John People * John the Baptist (died ), regarded as a prophet and the forerunner of Jesus Christ * John the Apostle (died ), one of the twelve apostles of Jesus Christ * John the Evangelist, assigned author of the Fourth Gospel, once identified with the Apostle * John of Patmos, also known as John the Divine or John the Revelator, the author of the Book of Revelation, once identified with the Apostle * John the Presbyter, a figure either identified with or distinguished from the Apostle, the Evangelist and John of Patmos Other people with the given name Religious figures * John, father of Andrew the Apostle and Saint Peter * Pope Jo ...
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