One of the great clashes among political theories is between realism and non-realism.
Raymond Geuss thinks so, regards non-realism as ascendant, but argues that realism is better. Here is how he distinguishes the two:
- Non-realism: it starts from, and is mostly concerned with, what people ought ideally or rationally to do, or to desire, or to be. Non-realism is an “ethics-first” approach: for Rawls justice comes first, or for Nozick rights come first.
- Realism: it starts from and is mostly concerned with “what really does move human beings” (9) and how institutions operate. A realist will “start from our existing motivations and our political and social institutions” (59). (Geuss mentions Lenin, Nietzsche and Weber in connection to realism.)
I would add one thing. That thing that really does move human beings, that set of existing motivations — it is human nature. Realism starts from human nature. Geuss really did not make this clear enough. This implies that realism is or should be Darwinian or evolutionary, for the best account of human nature by far is Darwinian.
Raymond Geuss, Philosophy and Real Politics (Princeton University Press, 2008).