l. Concept image and concept definition
The human brain is not a purely logical entity. The complex manner in which it
functions is often at variance with the logic of mathematics. It is not always
pure logic which gives us insight, nor is it chance that causes us to make
mistakes. To understand how these processes occur, both successfully and
erroneously, we must formulate a distinction between the mathematical
concepts as formally defined and the cognitive processes by which they are
conceived.
Many concepts which we use happily are not formally defined at all, we
learn to recognise them by experience and usage in appropriate contexts. Later
these concepts may be refined in their meaning and interpreted with increasing
subtlety with or without the luxury of a precise definition. Usually in this
process the concept is given a symbol or name which enables it to be
communicated and aids in its mental manipulation. But the total cognitive
structure which colours the meaning of the concept is far greater than the
evocation of a single symbol. It is more than any mental picture, be it pictorial,
symbolic or otherwise. During the mental processes of recalling and