Roderick Long posts an excellent two-part series (here and here) on Ayn Rand’s epistemology and its resemblance to Wittgenstein’s, of all people. Objectivist epistemology has never quite satisfied me. Rand rightly rejects the false dichotomy of nominalism and essentialism, and I can go along with concept-formation as selective attention, but she loses me, and Long, with her claim that all concepts involve measurement omission, particularly since she never supplies an example of how one might measure a highly abstract concept like justice or, to set the bar even higher, existence. (Peikoff, in Objectivism: The Philosophy of Ayn Rand, recognizes the difficulty. He has a crack at “thought,” which he supposes to be measurable by its content, intensity, effort and clarity, among other things, but he is not notably persuasive.) Rand gets entangled in one of the classic utilitarian problems: if we’re going to measure, or in this case omit to measure, we need units. Sometimes they’re available, sometimes not.
(Update: Ian Hamet comments.)