Article 4. Whether justice is in the will as its subject?

Anselm says (De Verit. xii) that "justice is rectitude of the will observed for its own sake." 

The subject of a virtue is the power whose act that virtue aims at rectifying. Now justice does not aim at directing an act of the cognitive power, for we are not said to be just through knowing something aright. Hence the subject of justice is not the intellect or reason which is a cognitive power. But since we are said to be just through doing something aright, and because the proximate principle of action is the appetitive power, justice must needs be in some appetitive power as its subject.

Now the appetite is twofold; namely, the will which is in the reason and the sensitive appetite which follows on sensitive apprehension, and is divided into the irascible and the concupiscible, as stated in I, 81, 2. Again the act of rendering his due to each man cannot proceed from the sensitive appetite, because sensitive apprehension does not go so far as to be able to consider the relation of one thing to another; but this is proper to the reason. Therefore justice cannot be in the irascible or concupiscible as its subject, but only in the will: hence the Philosopher (Ethic. v, 1) defines justice by an act of the will, as may be seen above (Article 1).

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