To constitute Justice and Injustice in acts, the acts must be voluntary; there being degrees of culpability in injustice according to the intention, the premeditation, the greater or less knowledge of circumstances. The act that a person does may perhaps be unjust; but he is not, on that account, always to be regarded as an unjust man (VIII.).
Here a question arises, Can one be injured voluntarily? It seems not, for what a man consents to is not injury. Nor can a person injure himself. Injury is a relationship between two parties (IX.). Equity does not contradict, or set aside, Justice, but is a higher and finer kind of justice, coming in where the law is too rough and general.
Book Sixth treats of Intellectual Excellences, or Virtues of the Intellect. It thus follows out the large definition of virtue given at the outset, and repeated in detail as concerns each of the ethical or moral virtues successively.
According to the views most received at present, Morality is an affair of conscience and sentiment; little or nothing is said about estimating the full circumstances and consequences of each act, except that there is no time to calculate correctly, and that the attempt to do so is generally a pretence for evading the peremptory order of virtuous sentiment, which, if faithfully obeyed, ensures virtuous action in each particular case. If these views be adopted, an investigation of our intellectual excellences would find no place in a treatise on Ethics. But the theory of Aristotle is altogether different. Though he recognizes Emotion and Intellect as inseparably implicated in the mind of Ethical agents, yet the sovereign authority that he proclaims is not Conscience or Sentiment, but Reason. The subordination of Sentiment to Reason is with him essential. It is true that Reason must be supplied with First Principles, whence to take its start; and these First Principles are here declared to be, fixed emotional states or dispositions, engendered in the mind of the agent by a succession of similar acts. But even these dispositions themselves, though not belonging to the department of Reason, are not exempt from the challenge and scrutiny of Reason; while the proper application of them in act to the complicated realities of life, is the work of Reason altogether. Such an ethical theory calls upon Aristotle to indicate, more or less fully, those intellectual excellences, whereby alone we are enabled to overcome the inherent difficulties of right ethical conduct; and he indicates them in the present Book, comparing them with those other intellectual excellences which guide our theoretical investigations, where conduct is not directly concerned.