The virtue of justice is particularly sensitive to all forms of indebtedness, not merely monetary. ‘The just deed,’ says St. Thomas with admirable succinctness, ‘is the deed that is adjusted to or commensurate with the other’ (S.T., II.II, Q. 57:3). For example, a parent feeds baby-food to her three-month-old baby because that is what the baby needs. The rest of the family receives normal food. An employer in a large company normally would not expect the daily cleaners to be doing executive work. Justice apportions expectations, services, and wages according to the needs, services, and abilities of the other.
Justice, therefore, does not mean that everyone is treated in the same way. Rather, it is the role of justice to see that people are treated differently when they are different, when they have different needs, and exist in differing situations. The equality with which justice is concerned involves ensuring that what is done for another or given to another is duly proportionate to that person in his or her situation of need.
At the same time, when people are existing in identical situations, then it is the role of justice to ensure that their treatment is identical. Two people performing the same job in the same company should be paid the same wage, regardless of the colour of their skin, their country of origin and so on. ‘Justice’, says Thomas Aquinas, ‘is the perpetual and constant will to render each one his right. A man is said to be just because he respects the rights of others’ (S.T. II.II. Q58:1).