ABSTRACT. I describe a prevalent approach to philosophical theorising as being a form of idealism. Conceptual idealism is the philosophical approach that maintains that for something to be possible is for it to fall under a possible concept. Conceptual realism denies this, maintaining that reality may outstrip our possible conception of it. Both philosophies are approaches to metaphysical theorising, but differ with regard to the nature and justification of a metaphysical theory. A third position, quietism, rejects the possibility of metaphysical truths for a particular domain of philosophical discourse. In addition to these very general considerations, conceptual realism and conceptual idealism also clash on more particular matters when it comes to issues of subjectivity.