> as lemmas

1903 B. Russell Princ. Math. i. 3 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.

1914 B. Russell Our Knowl. External World vii. 208 Such words as or, not, if, there is, identity, greater, plus, nothing, everything, function, and so on, are not names of definite objects, like ‘John’..but are words which require a context in order to have meaning... ‘Logical constants’, in short, are not entities.

1922 C. K. Ogden et al. tr. L. Wittgenstein Tractatus 69 My fundamental thought is that the ‘logical constants’ do not represent. That the logic of the facts cannot be represented.

1958 G. J. Warnock Eng. Philos. since 1900 x. 125 We thus get a distinction between so-called ‘logical constants’, the irreplaceable words on which the validity of general patterns of inference depends, and items of non-logical vocabulary.

1965 B. Mates Elem. Logic iv. 49 The logical constants occurring in ϕ are understood in the way usual among logicians (i.e., ‘∨’ as standing for ‘or’, ‘—’ for ‘not’, the universal quantifier for ‘all’, etc.).