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In logic and
analytic philosophy Analytic philosophy is a branch and tradition of philosophy using analysis, popular in the Western world and particularly the Anglosphere, which began around the turn of the 20th century in the contemporary era in the United Kingdom, United Sta ...
, an atomic sentence is a type of declarative sentence which is either true or false (may also be referred to as a
proposition In logic and linguistics, a proposition is the meaning of a declarative sentence. In philosophy, " meaning" is understood to be a non-linguistic entity which is shared by all sentences with the same meaning. Equivalently, a proposition is the no ...
, statement or
truthbearer A truth-bearer is an entity that is said to be either true or false and nothing else. The thesis that some things are true while others are false has led to different theories about the nature of these entities. Since there is divergence of o ...
) and which cannot be broken down into other simpler sentences. For example, "The dog ran" is an atomic sentence in natural language, whereas "The dog ran and the cat hid" is a molecular sentence in natural language. From a logical analysis point of view, the truth or falsity of sentences in general is determined by only two things: the logical form of the sentence and the truth or falsity of its simple sentences. This is to say, for example, that the truth of the sentence "John is Greek and John is happy" is a function of the meaning of " and", and the truth values of the atomic sentences "John is Greek" and "John is happy". However, the truth or falsity of an atomic sentence is not a matter that is within the scope of logic itself, but rather whatever art or science the content of the atomic sentence happens to be talking about. Logic has developed artificial languages, for example sentential calculus and predicate calculus, partly with the purpose of revealing the underlying logic of natural-language statements, the surface grammar of which may conceal the underlying logical structure. In these artificial languages an atomic sentence is a string of symbols which can represent an elementary sentence in a natural language, and it can be defined as follows. In a formal language, a well-formed formula (or wff) is a string of symbols constituted in accordance with the rules of syntax of the language. A term is a
variable Variable may refer to: * Variable (computer science), a symbolic name associated with a value and whose associated value may be changed * Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many ...
, an individual constant or a n-place function letter followed by n terms. An
atomic formula In mathematical logic, an atomic formula (also known as an atom or a prime formula) is a formula with no deeper propositional structure, that is, a formula that contains no logical connectives or equivalently a formula that has no strict subformul ...
is a wff consisting of either a sentential letter or an n-place
predicate Predicate or predication may refer to: * Predicate (grammar), in linguistics * Predication (philosophy) * several closely related uses in mathematics and formal logic: **Predicate (mathematical logic) **Propositional function **Finitary relation, o ...
letter followed by n terms. A sentence is a wff in which any variables are bound. An atomic sentence is an atomic formula containing no variables. It follows that an atomic sentence contains no
logical connective In logic, a logical connective (also called a logical operator, sentential connective, or sentential operator) is a logical constant. They can be used to connect logical formulas. For instance in the syntax of propositional logic, the binary co ...
s, variables or quantifiers. A sentence consisting of one or more sentences and a logical connective is a compound (or molecular) sentence.


Examples


Assumptions

In the following examples: * let ''F'', ''G'', ''H'' be predicate letters; * let ''a'', ''b'', ''c'' be individual constants; * let ''x'', ''y'', ''z'' be variables.


Atomic sentences

These wffs are atomic sentences; they contain no free variables or conjunctions: * ''F''(''a'') * ''G''(''a'', ''b'') * ''H''(''a'', ''b'', ''c'')


Atomic formulae

These wffs are atomic formulae, but are not sentences (atomic or otherwise) because they include free variables: * ''F''(''x'') * ''G''(''a'', ''z'') * ''H''(''x'', ''y'', ''z'')


Compound sentences

These wffs are compound sentences. They are sentences, but are not atomic sentences because they are not atomic formulae: * ∀''x'' (''F''(''x'')) * ∃''z'' (''G''(''a'', ''z'')) * ∃''x'' ∀''y'' ∃''z'' (''H''(''x'', ''y'', ''z'')) * ∀''x'' ∃''z'' (''F''(''x'') ∧ ''G''(''a'', ''z'')) * ∃''x'' ∀''y'' ∃''z'' (''G''(''a'', ''z'') ∨ ''H''(''x'', ''y'', ''z''))


Compound formulae

These wffs are compound formulae. They are not atomic formulae but are built up from atomic formulae using logical connectives. They are also not sentences because they contain free variables: * ''F''(''x'') ∧ ''G''(''a'', ''z'') * ''G''(''a'', ''z'') ∨ ''H''(''x'', ''y'', ''z'')


Interpretations

A sentence is either true or false under an interpretation which assigns values to the logical variables. We might for example make the following assignments: Individual constants * a: Socrates * b: Plato * c: Aristotle Predicates * Fα: α is sleeping * Gαβ: α hates β * Hαβγ: α made β hit γ Sentential variables * ''p'': It is raining. Under this interpretation the sentences discussed above would represent the following English statements: * ''p'': "It is raining." * ''F''(''a''): "Socrates is sleeping." * ''H''(''b'', ''a'', ''c''): "Plato made Socrates hit Aristotle." * ∀''x'' (''F''(''x'')): "Everybody is sleeping." * ∃''z'' (''G''(''a'', ''z'')): "Socrates hates somebody." * ∃''x'' ∀''y'' ∃''z'' (''H''(''x'', ''y'', ''z'')): "Somebody made everybody hit somebody." (They may not have all hit the same person z, but they all did so ''because'' of the same person x.) * ∀''x'' ∃''z'' (''F''(''x'') ∧ ''G''(''a'', ''z'')): "Everybody is sleeping and Socrates hates somebody." * ∃''x'' ∀''y'' ∃''z'' (''G''(''a'', ''z'') ∨ ''H''(''x'', ''y'', ''z'')): "Either Socrates hates somebody or somebody made everybody hit somebody."


Translating sentences from a natural language into an artificial language

Sentences in natural languages can be ambiguous, whereas the languages of the sentential logic and
predicate logic First-order logic—also known as predicate logic, quantificational logic, and first-order predicate calculus—is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science. First-order logic uses quantifi ...
s are precise. Translation can reveal such ambiguities and express precisely the intended meaning. For example, take the English sentence “Father Ted married Jack and Jill”. Does this mean Jack married Jill? In translating we might make the following assignments: Individual Constants * ''a'': Father Ted * ''b'': Jack * ''c'': Jill Predicates: * ''M''αβγ: α officiated at the marriage of β to γ Using these assignments the sentence above could be translated as follows: * ''M''(''a'', ''b'', ''c''): Father Ted officiated at the marriage of Jack and Jill. * ∃''x'' ∃''y'' (''M''(''a'', ''b'', ''x'') ∧ ''M''(''a'', ''c'', ''y'')): Father Ted officiated at the marriage of Jack to somebody and Father Ted officiated at the marriage of Jill to somebody. * ∃''x'' ∃''y'' (''M''(''x'', ''a'', ''b'') ∧ ''M''(''y'', ''a'', ''c'')): Somebody officiated at the marriage of Father Ted to Jack and somebody officiated at the marriage of Father Ted to Jill. To establish which is the correct translation of “Father Ted married Jack and Jill”, it would be necessary to ask the speaker exactly what was meant.


Philosophical significance

Atomic sentences are of particular interest in
philosophical logic Understood in a narrow sense, philosophical logic is the area of logic that studies the application of logical methods to philosophical problems, often in the form of extended logical systems like modal logic. Some theorists conceive philosophical ...
and the theory of truth and, it has been argued, there are corresponding atomic facts. An atomic sentence (or possibly the ''meaning'' of an atomic sentence) is called an elementary proposition by Ludwig Wittgenstein and an atomic proposition by
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell, (18 May 1872 – 2 February 1970) was a British mathematician, philosopher, logician, and public intellectual. He had a considerable influence on mathematics, logic, set theory, linguistics, ar ...
: * ''4.2 The sense of a proposition is its agreement and disagreement with possibilities of existence and non-existence of states of affairs. 4.21 The simplest kind of proposition, an elementary proposition, asserts the existence of a state of affairs.'' — Wittgenstein, '' Tractatus Logico-Philosophicus''. * ''A proposition (true or false) asserting an atomic fact is called an atomic proposition.'' — Russell, "Introduction to ''Tractatus Logico-Philosophicus''" * See also and especially regarding ''elementary proposition'' and ''atomic proposition'' as discussed by Russell and Wittgenstein Note the distinction between an ''elementary/atomic proposition'' and an ''atomic fact''. No atomic sentence can be deduced from (is not entailed by) any other atomic sentence, no two atomic sentences are incompatible, and no sets of atomic sentences are self-contradictory. Wittgenstein made much of this in his ''Tractatus''. If there are any atomic sentences then there must be "atomic facts" which correspond to those that are true, and the conjunction of all true atomic sentences would say all that was the case, i.e., "the world" since, according to Wittegenstein, "The world is all that is the case". (TLP:1). Similarly the set of all sets of atomic sentences corresponds to the set of all possible worlds (all that could be the case). The
T-schema The T-schema ("truth schema", not to be confused with " Convention T") is used to check if an inductive definition of truth is valid, which lies at the heart of any realisation of Alfred Tarski's semantic theory of truth. Some authors refer to it ...
, which embodies the theory of truth proposed by
Alfred Tarski Alfred Tarski (, born Alfred Teitelbaum;School of Mathematics and Statistics, University of St Andrews ''School of Mathematics and Statistics, University of St Andrews''. January 14, 1901 – October 26, 1983) was a Polish-American logician a ...
, defines the truth of arbitrary sentences from the truth of atomic sentences.


See also

* Logical constant


References


Bibliography

* Benson Mates, ''Elementary Logic'', Oxford University Press, 1972. * Elliot Mendelson, ''Introduction to Mathematical Logic'', Van Nostran Reinholds Company, 1964. {{Mathematical logic Predicate logic Sentences by type Syntax (logic) Propositions