Between the various types of rules which we shall give there will therefore be at once continuity of function and difference of structure. This rende… - Jean Piaget

This new philosophical psychology can in this respect be traced back to Maine de Biran, for even if in his time scientific psychology was unaware of its autonomy, and even if Biranian psychology was only critical of that of the empiricists, Biran believed in the Kantian distinction of noumena and phenomena and took care to limit his inquiry to the latter alone, which did not prevent him from extending it in the form of idealist speculations.

"Most instincts are allied to specialized organs, it is true, but it is nonetheless true that perception and acquired behavior, including the higher types of operative intelligence, do, in a more supple way, manifest certain functional possibilities or "reaction norms" of the anatomical and physiological structure of the species. In a word, the general coordinations of action upon which the building up of most basic types of knowledge is conditional, presuppose not only nervous coordinations but coordinations of a much more deep-seated kind, those which are, in fact, interactions dominating the entire morphogenesis."

The individual acts only if he experiences a need, i.e., if the equilibrium between the environment and the organism is momentarily upset, and action tends to re-establish the equilibrium, i.e., to re-adapt the organism (Claparède).