Any attempt to equalize the one-sided differentiation of the man of our times has to reckon very seriously with an acceptance of the inferior, because undifferentiated, functions. No attempt at mediation will be successful if it does not understand how to release the energies of the inferior functions and lead them towards differentiation. This process can take place only in accordance with the laws of energy, that is, a gradient must be created which offers the latent energies a chance to come into play.
Source - C.G. Jung, Schiller's Ideas on the Type Problem: The Superior and the Inferior Functions. CW 6: Psychological Types, par. 130.
In normal cases the inferior function remains conscious, at least in its effects; but in a neurosis it sinks wholly or in part into the unconscious. For, to the degree that the greater share of libido is taken up by the favored function, the inferior function undergoes a regressive development; it reverts to the [unconscious, powerfully tied to the collective] 'archaic' stage and becomes incompatible with the conscious, favored function. When a function that should normally be conscious lapses into the unconscious, its specific energy passes into the unconscious too. A function such as feeling possesses the energy with which it is endowed by nature; it is a well-organized living system that cannot under any circumstances be wholly deprived of its energy. So with the inferior function: the energy left to it passes into the unconscious and activates it in an unnatural way, giving rise to fantasies on a level with the archaicized function. In order to extricate the inferior function from the unconscious by analysis, the unconscious fantasy formations that have now been activated must be brought to the surface. The conscious realization of these fantasies brings the inferior function to consciousness and makes further development possible.
Source - C.G. Jung, Definitions (Inferior Function). Ibid., par. 764.
Art: Charles Dwyer, 'Cirque'