At some point in his life Piaget engaged with Kant and so appreciated a
priori and a posteriori propositions. A priori propositions depend upon or
relate to the nature of the universe we perceive: space, time, causation—
these are the necessary currency of perception and thought. We cannot
perceive the world without appreciating its three-dimensional nature or
explain events without appreciating that one action or event may be the
cause of another and that any sequence of causes functions in time. So
these a priori categories, because they are common to all human beings
and, as it were, built into our sensory and cognitive apparatus, must be
detectable in children. This implies that these a priori categories are devel-
oped during normal physical maturation and that it should be possible to
demonstrate by appropriate experiments how and when these categories
are formed.
Equally, there are other categories or concepts that are unique to indi-
viduals or to particular situations. Piaget developed the notions of accom-
modation and assimilation to characterize the relationship between the
organism and the environment. Whereas accommodation refers to the
adjustment by the organism to the environment, assimilation is centered
on the subject and his or her capacity to change cognitive structures to
interpret the environment. Thus, development is a perpetual alternation
between accommodating to an environment and assimilating it, and the
failure of the organism to deal with the environment by preexisting con-
cepts is what drives learning. Indeed learning, in one aspect, can be under-
stood as the extension of concepts over a new set of phenomena.
One writer described Piaget as “biologizing” Kant. 4 So we have here
the (in)direct testing of philosophical theories by a psychologist. If phil-
osophical theory is correct, certain psychological consequences will be
found in human beings and the formation of these consequences will be
observable as human beings grow from childhood. Piaget spoke of this as
“genetic epistemology.” For the philosopher, this is an exciting prospect
since it means that philosophical debate need not remain in the abstract
realm but may be tested out in ordinary lives. And this is nothing new
given that Marx believed that the task of philosophy was to change the
world rather than to analyze it.
In Kantian terms, “intuitions” (immediate sense impressions) without
concepts are “blind” (see Critique of Pure Reason ). Concepts are formed
by abstracting from numerous instances to create classifi catory categories
by which the continuous fl ow of sense impressions are reduced to manage-
able proportions and eventually understood. The child sees an animal in
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