Intellectual systems and movements are defined philosophically by means of their characteristic claims in the five major branches of philosophy: metaphysics, epistemology, human nature, ethics, and politics. As historical movements, they are defined by the time of their formulation and most vigorous activity.
So in the following table I offer a definitions of pre-modernism and modernism, each with the implicit genus “philosophical system” and a five-dimensional differentia.
Next: Defining post-modernism in contrast to modernism and pre-modernism.
[This chart is from Chapter 1 of Stephen Hicks’s Explaining Postmodernism: Skepticism and Socialism from Rousseau to Foucault (Scholargy Publishing, 2004, 2011). The full book is available in hardcover or e-book at Amazon.com. See also the Explaining Postmodernism page.]