The concept of discrimination picks out a kind of moral wrong that is a function of the salient social group membership of the person wronged: persons are treated as though they had diminished or degraded moral status on account of their group membership, or they are, because of their group membership and the relative disadvantages that they suffer due to that membership, made vulnerable to domination and oppression. But why have such a concept? Why not simply have the concepts of domination, oppression, and degrading treatment, abstracting from whether or not the reasons for such wrongs involve group membership?
Until the middle of the 19th century, critical moral reflection and discussion proceeded largely without the concept of discrimination. But over the course of the first half of the 20th century, moral reflection became increasingly sensitive to the fact that many, even most, of the large-scale injustices in history had a group-based structure: certain members of society were identified by others as belonging to a particular salient group; the group members were consistently denigrated and demeaned by the rest of society and by its official organs; and many serious relative disadvantages connected to this denigration and demeaning, such as material deprivation and extreme restrictions on liberty, were imposed on the members of the denigrated group. It is this historical reality, apparently deeply rooted in human social life, that gives the concept of discrimination its point and its usefulness.
The concept highlights the group-structure, and the relative deprivations built around this structure, that are exhibited by many of the worst systematic wrongs that humans inflict on one another.
At the same time, the group structure of these injustices does not mean that the group as such is the party that is wronged; rather, the wrongs are ultimately wrongs to the individual persons making up the group. Accordingly, the concept of discrimination has become a useful tool for representing many serious wrongs, while avoiding the implication that these wrongs are ultimately done to the groups as such.