Jean Piaget (1896-1980) was a Swiss developmental psychologist known for his epistemological studies with children. His theory of cognitive development and epistemological view are known as "genetic epistemology".
He states in the Preface, "A book on the 'Psychology of Intelligence' could cover half the realm of psychology. The following pages are confined to outlining one view, that based on the formation of 'operations,' and to determing as objectively as possible its place among others which have been put forward."
Here are some representative quotations from the book:
"Every psychological explanation comes sooner or later to lean either on biology or on logic (or on sociology, but this in turn leads to the same alternatives)."
"And, furthermore, even if stages of development simply mark successive approximations of intelligence in its conquest of immutable 'ideas'; what proof have we that the normal adult or the logicians of Russell's school have succeeded in grasping them and will not be continually surpassed by future generations?"
"Formal logic is, according to this view, not an adequate description for the whole of living thought; formal operations constitute solely the structure of the final equilibrium to which concrete operations tend when they are reflected in more general systems linking together the propositions that express them."
"But, granting all this and admitting that logical thought is necessarily social, the fact remains that the laws of grouping constitute general forms of equilibrium which express both the equilibrium of inter-individual interaction and that of the operations which every socialized individual is capable when he reasons internally in terms of his most personal and original ideas."