It is vain, therefore, to look for clearly defined and systematic presentations of the idea among ancient writers.
In his Psychology Herbart rejects altogether the doctrine of mental faculties as one refuted by his metaphysics, and tries to show that all psychical phenomena whatever result from the action and interaction of elementary ideas or presentations (Vorstellungen).
The soul being one and simple, its separate acts of self-preservation or primary presentations must be simple too, and its several presentations must become united together.
But otherwise there ensues a conflict in which the opposed presentations comport themselves like forces and mutually suppress or obscure each other.
The first must obviously be as small as possible; thus for two totally-opposed presentations a and b, of which a is the greater, the inhibendum = b.