It is easy to suppose that “individual”, “particular”, “complex” etc. are primitive ideas of logic. Russell e.g. says “individual” and “matrix” are “primitive ideas”. This error presumably is to be explained by the fact that, by employment of variables instead of the generality-sign it comes to seem as if logic dealt with things which have been deprived of all properties except thing-hood, and with propositions deprived of all properties except complexity. We forget that the indefinables of symbols [Urbilder von Zeichen] only occur under the generality-sign, never outside it.

Ts-201a2,b24