 Madhyamakālaṃkāra begins with the observation that if a phenomenon has an essential nature, then either that nature is simple or complex, that is, it is either a single thing or many things; there is no third possibility. This leads to discussions of doctrines by several schools of Indian philosophy, both Buddhist and non-Buddhist. Each of the schools examined posits at least one entity that is completely uniform in nature and therefore has no internal differentiations. Several schools posit a uniform entity that is said to be the single source of all multiplicity. Drawing on arguments by earlier Buddhist thinkers such as Dharmakīrti, Śāntarakṣita argues that if there were a uniform, permanent and unobstructed singularity, then everything it supposedly causes would have to exist all the time. A cause is something in the presence of which an effect arises and in the absence of which the effect does not arise. But if a cause is permanent, then it is never absent, so none of its putative effects can ever be absent. In a theory that posits a single permanent cause of all things, there is no satisfactory account of all the changes that are experienced in daily life, nor is there any satisfactory account of temporal sequences or the fact that things exist in some places but not in others. This argument is applied to discredit the Sāṃkhya doctrine of primordial matter, the Nyāya doctrine of God, and the Vedāntin doctrine of Brahman. It is also applied to the Yogācāra doctrine that all things arise from consciousness. After arguing against the main candidates for singularity nominated by the various schools, Śāntarakṣita turns his attention to multiplicity. The very idea of multiplicity, he notes, only makes sense if one is talking about a collection of singularities. Given, however, that there are no singularities, there cannot be any collection of them. This being the case, no inherent nature of any entity can be either singular or multiple; if an entity has neither a singular nor a multiple inherent nature, it has no inherent nature at all. In other words, all phenomena are empty of inherent natures.