For beatitude is man's ultimate perfection. But everything is perfect in so far as it is actually (actu, i.e. in realized actuality): for potentiality without actuality is imperfect. Therefore beatitude should consist in man's ultimate actuality. But manifestly action (operatio) is the final actuality of the actor (operantis); as the Philosopher shows, demonstrating that everything exists for its action (propter suam operationem). Hence it follows of necessity that man's beatitude is action."
The next point to consider is whether beatitude is the action of man's senses or his intellect. Drawing distinctions, Thomas points out that
"the action of sense cannot pertain to beatitude essentially; because man's beatitude essentially consists in uniting himself to the increate good; to which he cannot be joined through the action of the senses. Yet sense-action may pertain to beatitude as an antecedent or consequence: as an antecedent, for the imperfect beatitude attainable in this life, where the action of the senses is a prerequisite to the action of the mind; as a consequence, in that perfect beatitude which is looked for in heaven; because, after the resurrection, as Augustine says, from the very beatitude of the soul, there may be a certain flowing back into the body and its senses, perfecting them in their actions. But not even then will the action by which the human mind is joined to God depend on sense."
Beatitude then is the action of man's intellectual part; and Thomas next inquires, whether it is an action of the intelligence or will (intellectus aut voluntatis). With this inquiry we touch the pivot of Thomas's attitude, wherein he departs from Augustine, in apparent reliance on the word of John: "This is eternal life that they should know thee, the one true God." Life eternal is man's final end; and therefore man's beatitude consists in knowledge of God, which is an act of mind. Thomas argues this at some length. He refers to the distinction between what is essential to the existence of beatitude, and what is joined to it per accidens, like enjoyment (delectatio).
"I say then, that beatitude in its essence cannot consist in an act of will. For it has appeared that beatitude is the obtaining (consecutio) of the final end. But obtaining does not consist in any act of will; for will attaches to the absent when one desires it, as well as to the present in which one rests delighted. It is evident that the desire for an end is not an obtaining of it, but a movement
