James Mark Baldwin, answered from the texts and cited to the page.
Knowledge is not a finished thing dropped into the mind, nor are the categories of thought — substance, cause, self, number, truth — eternal forms given in advance. They are grown; they have a history in the mind of the child as surely as the body has an embryology, and to understand what a category is you must watch how it comes to be. This is genetic epistemology: the study of knowledge through the stages of its actual development, from the infant's first sensori-motor dealings with things up through the reflective, logical thought of the adult.
Each stage grows out of the one before by determinable processes — assimilation of the new to the old, accommodation of the old to the new — and the logic of the finished mind is the last term of a genetic series, not its presupposition. The philosopher who would define truth or the self or the object without tracing its genesis is describing a cross-section of a growth and mistaking it for the whole. Give me the sequence of stages, and I will show you the making of knowledge itself.12
In all these cases, however, there is again a greater and a less exactness. The topics with the reports of results which I am going on to give may be taken, however, as typical, and as showing the direction of complete knowledge rather than as having in any one case approached it. Before we take up particular questions, however, a word may be allowed upon the general bearings of the study of the child's mind.The Story of the Mind, pp. 53–54
The only way to avoid this is to The Natural Fiistory of the Categories 281 say that reality has neither forward nor backward refer- ence. So say the idealists in getting thought which is not in time. But be that as it may, we are dealing with experience, though for myself, I must say, thought which looks neither backward nor forward is no thought at all. 7.Development and Evolution
Genetic epistemology is Baldwin's most enduring idea: Jean Piaget adopted the name, the program, and Baldwin's key terms (assimilation, accommodation, the stage sequence) and built the most influential developmental theory of the twentieth century on them. The standing philosophical objection is the genetic fallacy — that the psychological origin of a belief or category is irrelevant to its logical validity or truth, so that a genetic account of knowledge cannot be an epistemology in the normative sense. Baldwin and his heirs answer that the objection assumes the very separation of the logical from the genetic that a developmental theory of knowledge denies; the debate between the normative and the genetic understanding of knowledge remains open, and the developmental study of cognition Baldwin founded is a permanent field.