plasticity of psychic development is not without limits as to its direction; one can describe it as a special capacity for retrograde action or regression, for it sometimes happens that a later and higher stage of development that has been abandoned cannot be attained again. But the primitive conditions can always be reconstructed; the primitive psyche is in the strictest sense indestructible.
The so-called mental diseases must make the impression on the layman of mental and psychic life fallen into decay. In reality the destruction concerns only later acquisitions and developments. The nature of mental diseases consists in the return to former states of the affective life and function. An excellent example of the plasticity of the psychic life is the
32
