It does not follow from this that human perfection is perfect self-realisation, in the sense of every power being realised to the utmost. The powers of man are many, not all of equally high quality. The utmost realisation of one might and would interfere with the realisation of another: the baser might be brought out to the loss of nobler and better: the perfection of man is a harmony of powers, which implies both use and restraint of them severally according to the excellence of their several functions. In man, much must be left in potentiality, if the best actuality that he is capable of is to be realised. In an orchestra, where every instrument played (or brayed) continuously at its loudest, the result would be din indescribable, a maximum of noise with a minimum of music. Perfection is actuality up to standard. In a finite nature, the standard imposes limitations, according to the Aristotelian canon of the golden mean, a canon not framed for the infinite.

Of God and His Creatures: 1.28