Since in every kind of being there is a supreme possible good, and since man too is a certain kind [lit. species] of being, there must be a supreme possible good for man. I do not speak of a good which is supreme in the absolute sense, but one that is supreme for man; for the goods which are accessible to man are limited and do not extend to infinity. By reason let us seek to determine what the supreme good is which is accessible to man.

The supreme good for man should be in terms of his highest power, and not according to the vegetative soul, which is [also] found in plants, nor according to the sensitive soul, which is [also] found in animals and from which their sensual pleasures arises. But man’s highest power is his reason and intellect. For this is the supreme director of human life both in the order of speculation and in the order of action. Therefore, the supreme good attainable by man must be his by means of his intellect. Therefore, men who are so weighed down by sense pleasures that they lose intellectual goods should grieve. For they never attain their supreme good. They are so given to the senses that they do not seek that which is the good of the intellect itself. Against these the Philosopher protests, saying: “Woe to you men who are numbered among beasts and who do not attend to that which is divine within you!” He calls the intellect that which is divine in man. For if there is anything divine in man, it is right for it to be the intellect. Just as that which is best among all beings is the divine, so also that which is best in man we call divine.

Moreover, one power of the human intellect is speculative and the other practical. This is clear from this fact, that man theorises about certain objects which he does not actively cause, for example, eternal things, and actively causes others under the intellect’s direction whereby he realises a means which can be chosen in human acts. From this, then, we know in general that these two intellectual powers are present in man.