P27: The greatest satisfaction of Mind there can be arises from this third kind of knowledge.

Dem.: The greatest virtue of the Mind is to know God/Nature (by IVP28), or to understand things by the third kind of knowledge (by P25). Indeed, this virtue is the greater, the more the Mind knows things by this kind of knowledge (by P24). So he who knows things by this kind of knowledge passes to the greatest human perfection, and consequently (by Def. Aff. II), is affected with the greatest Joy, accompanied (by IIP43) by the idea of himself and his virtue.

Therefore (by Def. Aff. XXV), the greatest satisfaction there can be arises from this kind of knowledge, q.e.d.