 McTaggart also rejected the less radical version of monism that holds that there is only one substance. In first volume of the Nature of Existence, sections 65 and 73, McTaggart defined “substance” as that which has features without being a feature. In his later article, “an Ontological Idealism”, he defines “substance” as that which has features without being a feature or having a feature as a part. The reason for the revision is that at this point in McTaggart’s career, he accepted the existence of facts construed as complexes of particulars and properties. Facts satisfy the older definition of “substance” but not the newer one. McTaggart argues that we perceive that there are many substances, but also holds that it is a priori that, if there is one substance, then there are many, since it is a priori that every substance has infinitely many parts. McTaggart also rejected solipsism understood as the view that reality consists of a single person, which although infinitely divided is such that nothing exists that is not a part of him. Solipsism thus understood is strictly compatible with the existence of a plurality of substances; however, McTaggart held that solipsism was ruled out by the requirement that there be a relation of determining  correspondence.[34]