 Mereological Doctrines. McTaggart holds the following doctrines concerning the part-whole relation as it applies to substances. First, McTaggart endorses unrestricted composition: whenever there are some substances, there is a further substance that is composed of them. McTaggart dismisses the worry that unrestricted composition implies that there are bizarre substances such as the substance composed of all the readers of the SEP and the moon. (See chapter 16 of the first volume of the Nature of Existence.) For this reason, McTaggart holds that there is a substance that is composed of everything that there is. He calls this substance “the Universe”. (See section 77 and chapter 18 of the first volume of the Nature of Existence.)