Abstract The thesis is that the explicit adequate development of the science of knowing will require the use of the mathematical theory of categories. Even within mathematical experience, only that theory has approximated a particular model of the general, sufficient as a foundation for a general account of all particulars. Arising 50 years ago from the needs of geometry, category theory has developed such notions as adjoint func•• tor, topos, fibration, closed category, 2-category, etc., in order to provide: (1) A guide to the complex, but very non-arbitrary constructions of the concepts and their interactions which grow out of the study of space and quantity. It was only the relentless adherence to the needs of that basic subject that made category theory so well-determined yet powerful. When some schools of category theory have gone astray, it has usually been due either to neglecting too long that specific goal of studying space and quantity better, or to ossifying some partial determination of what space and quantity are. If we replace “space and quantity” in (1) above by “any serious object of study,” then (1) becomes my working definition of objective logic.