Virtus est in potentia animae quia perfectio est in eo cuius est perfectio.
Virtue is in a power of the soul because perfection is in that which it perfects.
Omnis operatio est ab anima per aliquam potentiam.
All operation proceeds from the soul through a power.
Disponit ad optimum: optimum autem est finis, qui vel est operatio rei, vel aliquid consecutum per operationem a potentia egredientem.
Virtue disposes to that which is best: for the best is the end, which is either a thing's operation, or something acquired by an operation proceeding from the thing's power.
Unde virtus humana est in potentia animae sicut in subiecto.
Therefore a power of the soul is the subject of virtue.