To the second one proceeds thus. It seems that habitudes are not distinguished according to objects. For contraries differ in species, but the same habitude of knowledge is of contraries, as medicine of the healthy and the sick. Therefore it is not according to objects differing in species that habitudes are distinguished.
Further, diverse kinds of knowledge are diverse habitudes. But the same knowable pertains to diverse kinds of knowledge, just as both the physicist and the astronomer demonstrate that the earth is round, as is said in Phys. II. Therefore habitudes are not distinguished according to objects.
Further, to the same act is the same object. But the same act can pertain to diverse habitudes of virtue, if it is referred to diverse ends, as giving money to someone, if it is for the sake of God, pertains to charity; but if it is for the sake of paying a debt, it pertains to justice. Therefore the same object is able to pertain to diverse habitudes. Therefore there is no diversity of habitudes according to diversity of objects.
But contrariwise, acts differ in species according to diversity of objects, as was said above. But habitudes are sorts of dispositions to acts. Therefore habitudes are also distinguished according to diverse objects.
I reply that it must be said that habitude both is a sort of form and also habitude. Therefore distinction of habitudes according to species is able to be considered either according to the common way by which forms are distinguished in species or according to the proper way of distinguishing habitudes. Forms are indeed distinguished from each other according to diverse active principles, since every agent makes what is like according to species. Now habitude implies ordering to something. But everything that is said according to ordering to something, is distinguished according to the distinction of those to which it is said. And habitude is a sort of disposition ordered to two things, that is to nature and to working according to nature. Thus according to the three, habitudes are distinguished in species: In one way, according to the active principles of such dispositions; in another way, according to nature; but in a third way, according to specifically differing objects; as will be explained in the following.
To the first therefore it must be said that in distinction of powers or even habitudes, the object itself is not to be considered materially, but the notion of the objects differing in species or even in genus. But although contraries differ in species in the diversity of things, yet the same notion is for cognizing both, because one is cognized through the other. And therefore inasmuch as they converge in one cognizable notion, they pertain to one cognitive habitude.
To the second it must be said that the physicist demonstrates that the earth is round through some middle term, and the astronomer through another, for the astronomer demonstrates this through mathematical middle terms, as by the shapes of eclipses, but the physicist demonstrates it through natural middle terms, as by change of the heavy toward the middle, or somesuch. But the whole impulse of demonstration, which is deduction [syllogismus] making to know, as was said in Poster. I, hangs on the middle term. And thus middle terms are like diverse active principles according to which habitudes of kinds of knowledge are diversified.
To the third it must be said that, as the Philosopher says in Physic. II and in Ethic. VII, the end is in workables as the principle is in demonstratives. And so the diversity of ends diversifies virtues just like the diversity of active principles. And the ends themselves are objects of interior acts, which pertains most of all to virtues, as is obvious from what was said above.
[Thomas Aquinas, ST 2-1.54.2, my translation. The Latin is here, the Dominican Fathers translation is here.]
