Thus the right hand is by nature more powerful than the left; yet it is possible that all men may become ambidextrous.

Those regulations of justice that are not by nature, but by human appointment, are not the same everywhere; nor is the political constitution everywhere the same; yet there is one political constitution only that is by nature the best everywhere (VII.).
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.).