Logical activity is not the whole of intelligence. One can be intelligent without being particularly logical.

The main functions of intelligence, that of inventing solutions and that of verifying them, do not necessarily involve one another. The first partakes of imagination; the second alone is properly logical.

“Intelligence is what you use when you don't know what to do.”

Logical reasoning is an argument which we have with ourselves and which reproduces internally the features of a real argument.

It is with children that we have the best chance of studying the development of logical knowledge, mathematical knowledge, physical knowledge, and so forth.

Logical positivists have never taken psychology into account in their epistemology, but they affirm that logical beings and mathematical beings are nothing but linguistic structures.