The author contends that the Objectivist epistemology has lacked a viable model of propositional knowledge for nearly fifty years, due to neglect of Rand's unit-perspective view of concepts. This pioneering insight, he says, not only is an essential building block of her concept theory, but also welds together the three levels of logical theory and provides the clearest X-ray picture of our multilayered conceptual knowledge. Using the unit-perspective to expand Rand's theory of concepts, the author then devises a theory of (...) the proposition, giving considerable attention to axioms and statements about nonexistent subjects. (shrink)