Asked • 03/14/19

What is the difference between a statement and a proposition?

I'm doing a MOOC on mathematical philosophy and the lecturer drew a distinction between a proposition and a statement. This is very puzzling to me. My background is in math and I regard those two words as synonymous. I looked on Wikipedia and it says: *Often propositions are related to closed sentences to distinguish them from what is expressed by an open sentence. In this sense, propositions are "statements" that are truth bearers. This conception of a proposition was supported by the philosophical school of logical positivism.* http://en.wikipedia.org/wiki/Proposition This also went right over my head. I (naively) regard both a proposition and a statement to be well-formed formulas that, once a suitable interpretation is chosen, have the ability to be either true or false. For example 2 + 2 = 4 is a proposition or statement because once I assume the Peano axioms along with the usual interpretations of the symbols '2', '4', '+', and '=', this statement is capable of being determined to be true or false. Can anyone shed some light?

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Hien B. answered • 03/21/19

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Gek Hua T.

i am shocked and surprised that the claim "statements are synonymous with sentences" is made. while a statement is expressible by a sentence and is either true or false ... a sentence like "Hien B. is stupid" can be neither true nor false (since stupidity is subjective and most important of all ... the context has not been established. Hien B. maybe clever in certain things but looks stupid to many others in other area).
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11/22/21

Majid S.

Hien B. has a point. Example: “y > 5” is a statement but not a proposition because Its truth value depends on the value of y, but this value is not specified, so I cannot evaluate the truthiness or falsehood of it. We call this type of statement a propositional function or open sentence.
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10/02/22

Majid S.

Also, statements are synonymous with sentences rather than propositions because not every statement can be treated straightforwardly as a proposition! Example, if you believe that "if a shape is a square, then it is a rectangle" How can this be evaluated then? Basically, we have two predicates here: S(x) standing for “x is a square” and R(x) standing for “x is a rectangle”. The sentence we are looking at is, S(x) → R(x). This is basically neither true nor false, as it is not a statement. Although we all know that we meant to consider the statement, ∀x(S(x) → R(x)). See Levin (http://discrete.openmathbooks.org/dmoi3.html)
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10/02/22

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