"Put simply, the main insight of the Vaiśeṣika is that consciousness is not to be found as a property that emerges out of matter. The best analogy to understand it is to take reality as a coin of which one side is physical matter and the other side is consciousness, and ordinarily neither may be reduced to the other. Kaṇāda says that consciousness cannot be a substance for it is not something that is modified by time or space, and therefore it should be a separate ontological category."