Summa theologiae IIaIIae 57: On right

Here there are four things to consider:

1. Whether right is the object of justice

2. Whether right is suitably divided into natural and positive right

3. Whether the ius gentium is the same as natural right

4. Whether paternal right and dominative right should be regarded as distinct species of right

articulus 1: Whether right [ius] is the object of justice [iustitia]

It seems that right is not the object of justice.

obiectio 1: For the jurist Celsus says that ‘right is the art of the good and equal’. But an art is not the object of justice, because art is an intellectual virtue in itself. Therefore right is not the object of justice.

obiectio 2: Moreover, Isidore says in the book Etymologies that ‘Law is a species of right.’ But the Philosopher identifies ‘legislative wisdom’ as one of the parts of practical wisdom [prudentia]. Hence law is the object not of justice, but of practical wisdom. Therefore right is not the object of justice.

obiectio 3: Moreover, the chief purpose of justice is to make a man subject to God; for in the book De moribus ecclesiae Augustine says that ‘justice is love serving God alone, and hence governing rightly all things subject to man’. But right [ius] does not pertain to things Divine, but only to things human; for Isidore, in the book Etymologies, says that ‘fas is the Divine law, and ius the human law’. Therefore right is not the object of justice.