Everything about Proposition totally explained
In
philosophy and
logic,
proposition refers to the content or meaning of an
assertion, or the string of symbols, marks, or grunts that make up a written or spoken declarative sentence. In either usage, propositions are meant to be the truth-bearers (i.e they're what is either
true or
false).
The existence of propositions (in usage (a) above), and the existence of meanings is disputed, and where admitted their nature is controversial. In earlier texts writers have not always made it sufficiently clear whether they're using the term
proposition in sense (a) or (b). To avoid the controversies and ontological implications, the term
sentence is often now used instead of
proposition or
statement to refer to just those strings of symbols that are truth-bearers, being either true or false under an interpretation.
Common usage
Different sentences are used to express the same proposition when they both have the same meaning. For example, "Snow is white" (in English) and "Schnee ist weiß" (in German) are different sentences, but both say the same thing, that snow is white. Hence, it's argued that they express the same proposition. Two different sentences in the same language may also be said to express the same proposition. For example, "Tiny crystals of frozen water precipitation are white" is a sentence in English, but may be said to express the same proposition as the sentence "Snow is white" by virtue of the definition of snow.
Historical usage
Usage in Aristotle
Aristotelian logic identifies a proposition as a sentence which affirms or denies the
predicate of a
subject. An Aristotelian proposition may take the form "All men are mortal" or "Socrates is a man." Such propositions comprise the atomic elements in
Propositional logic. The sentence "A and B" expresses both proposition A and proposition B. Both treat the proposition as a sentence having the aforementioned form. Such usage is increasingly non-standard.
Usage by the Logical Positivists
Often propositions are related to closed
sentences, to distinguish them from what is expressed by an open sentence, or
predicate. In this sense, propositions are statements that are either
true or false. This conception of a proposition was supported by the philosophical school of
logical positivism.
Some philosophers, such as
John Searle, hold that other kinds of speech or actions also assert propositions. Yes-no
questions are an inquiry into a proposition's truth value.
Traffic signs express propositions without using speech or written language. It is also possible to use a declarative sentence to express a proposition without asserting it, as when a teacher asks a student to comment on a quote; the quote is a proposition (that is, it has a meaning) but the teacher isn't asserting it. "Snow is white" expresses the proposition that snow is white without asserting it (for example claiming snow is white).
Propositions are also spoken of as the
content of
beliefs and similar
intentional attitudes such as desires, preferences, and hopes. For example, "I desire
that I've a new car," or "I wonder
whether it'll snow" (or, whether it's the case "that it'll snow"). Desire, belief, and so on, are thus called propositional attitudes when they take this sort of content.
Usage by Russell
Bertrand Russell held that propositions were structured entities with objects and properties as constituents. Others have held that a proposition is the set of possible worlds/states of affairs in which it's true. One important difference between these views is that on the Russellian account, two propositions that are true in all the same states of affairs can still be differentiated. For instance, the proposition that two plus two equals four is distinct on a Russellian account from three plus three equals six. If propositions are sets of possible worlds, however, then all mathematical truths are the same set (the set of all possible worlds).
Relation to the mind
In relation to the mind, propositions are discussed primarily as they fit into
propositional attitudes. Propositional attitudes are simply attitudes characteristic of
folk psychology (belief, desire, etc.) that one can take toward a proposition (for example 'it is raining', 'snow is white', etc.). In English, propositions usually follow folk psychological attitudes by a "that clause" (for example "Jane believes
that it's raining"). In
philosophy of mind and
psychology, mental states are often taken to primarily consist in propositional attitudes. The propositions are usually said to be the "mental content" of the attitude. For example, if Jane has a mental state of believing that it's raining, her mental content is the proposition 'it is raining'. Furthermore, since such mental states are
about something (namely propositions), they're said to be
intentional mental states. Philosophical debates surrounding propositions as they relate to propositional attitudes have also recently centered on whether they're internal or external to the agent or whether they're mind-dependent or mind-independent entities (see the entry on
internalism and externalism in philosophy of mind).
Treatment in logic
As noted above, in
Aristotelian logic a proposition is a particular kind of sentence, one which affirms or denies a
predicate of a
subject. Aristotelian propositions take forms like "All men are mortal" and "Socrates is a man."
In mathematical logic, propositions, also called
propositional formulas, are the elements in the domain of
propositional logic. The sentence
A and B expresses both proposition A and proposition B.
Objections to propositions
A number of philosophers and linguists claim that the notion of a proposition is too vague or not useful. For them, it's just a misleading concept that should be removed from philosophy and
semantics.
W.V. Quine maintained that the indeterminacy of translation prevented any meaningful discussion of propositions, and that they should be discarded in favor of
sentences.
Further Information
Get more info on 'Proposition'.
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