Justice, then, is a central part of ethics and should be given due consideration in our moral lives. In evaluating any moral decision, we must ask whether our actions treat all persons equally. If not, we must determine whether the difference in treatment is justified: are the criteria we are using relevant to the situation at hand? But justice is not the only principle to consider in making ethical decisions. Sometimes principles of justice may need to be overridden in favor of other kinds of moral claims such as rights or society's welfare. Nevertheless, justice is an expression of our mutual recognition of each other's basic dignity, and an acknowledgement that if we are to live together in an interdependent community we must treat each other as equals.
Locke attacks both the view that we have any innate principles (for example, the whole is greater than the part, do unto others as you would have done unto you, etc.) as well as the view that there are any innate singular ideas (for example, God, identity, substance, and so forth). The main thrust of Locke’s argument lies in pointing out that none of the mental content alleged to be innate is universally shared by all humans. He notes that children and the mentally disabled, for example, do not have in their minds an allegedly innate complex thought like “equals taken from equals leave equals”. He also uses evidence from travel literature to point out that many non-Europeans deny what were taken to be innate moral maxims and that some groups even lack the idea of a God. Locke takes the fact that not all humans have these ideas as evidence that they were not implanted by God in humans minds, and that they are therefore acquired rather than innate.