This can be done only through ecstasy, the supreme degree of virtue. In the state of ecstasy man remains passive and unconscious of everything except his union with the One. This is the supreme state of happiness for man. As in all great systems in Greek philosophy, the theory of knowledge in Plotinus corresponds to his theory of being. The knowledge of reason is discerning and deals with ideas and the essences of things.
Intellective knowledge is knowledge of self, obtained through auto-contemplation.
The knowledge which crowns our mental activity is ecstatic or knowledge of the One. It is acquired not by virtue of the powers of the intellect but through God. Between God and matter Plotinus placed emanations, but in order to justify all religions he also admitted intermediary demons or spirits. His successor Porphyry arranged and published Plotinus' works. Later Proclus and Iamblichus developed the theory of demons and were the advocates of a mysterious kind of knowledge called gnosis.