Full Idea
He who by thought can penetrate within his own substance, and can thus acquire knowledge of it, finds himself in this actualisation of knowledge and consciousness, where the substrate that knows is identical with the object that is known.
Gist of Idea
Successful introspection reveals the substrate along with the object of thought
Source
Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 44)
Book Reference
Porphyry: 'Launching Points to the Realm of the Mind', ed/tr. Guthrie,Kenneth [Phanes 1988], p.68
A Reaction
It seems remarkably that this ability is confidently asserted by Porphyry, and flatly denied by Hume. Were they just different people, or were they looking for different things, or was one of them deluded?
Related Idea
Idea 1316 Introspection always discovers perceptions, and never a Self without perceptions [Hume]