So, on the face of it, this thesis has here been inferred from Leibniz’ Law. Moore observes, however, that the step from (1) to (2) is invalid; it confuses the necessity of a connection with the necessity of the consequent. In ordinary language this distinction is not clearly marked, although it is easy to draw it with a suitable formal language.
Moore’s argument here is a sophisticated piece of informal modal logic; but whether it really gets to the heart of the motivation for Bradley’s Absolute idealism can be doubted. My own view is that Bradley’s dialectic rests on a different thesis about the inadequacy of thought as a representation of reality, and thus that one has to dig rather deeper into Bradley’s idealist metaphysics both to extract the grounds for his monism and to exhibit what is wrong with it.
Interesting. GE Moore is in good company, along with Leibniz.