Professor DeMarco received his Ph.D. in 1969 from The Pennsylvania State University, after which he taught at Tuskegee Institute before moving to Cleveland State in 1972. He writes in political philosophy, ethics, the social thought of W.E.B. DuBois, and on Charles S. Peirce's pragmatism.

His books include A Coherence Theory in Ethics, Moral Theory, The Social Thought of W.E.B. DuBois and Moral Reasoning (with R.M. Fox). He is also co-editor of New Directions in Ethics (also with Richard M. Fox).

DeMarco is active in multimedia and Web production. His logic tutorial, Learning Logic (produced with Patrick Hurley), is distributed by Cengage.

His viewpoint in ethics centers on a coherence approach, meaning that the mark of a correct position in ethics is how well it can hold together our moral values and judgments. This view allows him to find a role for most moral theories, and he rejects giving any one theory an edge over all others. A brief account of his position is found in "Coherence and Applied Ethics," in the Journal of Applied Philosophy (1997), pages 289-300