If I cannot say a priori what elementary propositions there are, then the attempt to do so must lead to obvious nonsense. (5.5571)
Ludwig Wittgenstein
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Propositions are truth-functions of elementary propositions. (An elementary proposition is a truth-function of itself.) (5)
Ludwig Wittgenstein
A truly rational theory would allow us to deduce the elementary particles (electron,etc.) and not be forced to state them a priori.
Albert Einstein
Notwithstanding their attacks on the basic conception of rationalism, on synthetic a priori judgments, that is, material propositions that cannot be contradicted by any experience, the empiricist posits the forms of being as constant.
Max Horkheimer
Wherever Mathematics is mixed up with anything, which is outside its field, you will find attempts to demonstrate these merely conventional propositions a priori, and it will be your task to find out the false deduction in each case.
Carl Gustav Jacob Jacobi
Pure Mathematics is the class of all propositions of the form “p implies q,” where p and q are propositions containing one or more variables, the same in the two propositions, and neither p nor q contains any constants except logical constants. And logical constants are all notions definable in terms of the following: Implication, the relation of a term to a class of which it is a member, the notion of such that, the notion of relation, and such further notions as may be involved in the general notion of propositions of the above form. In addition to these, mathematics uses a notion which is not a constituent of the propositions which it considers, namely the notion of truth.
Bertrand Russell
Wittgenstein, Ludwig
Wodehouse, P. G.
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