Monism is the idea that everything is, or is ultimately reducible to, one. This is not quite the same as nondualism, a term increasingly common in mystical circles. Nondualism is the idea that everything is not two or more – not more than one. Nondualism and monism are very similar concepts, but they’re not exactly the same.

I’m speaking here of each term’s deepest metaphysical meaning, where it refers to the ultimate nature of the universe (each term can be used in other ways as well). The general core idea of nondualism is quite widespread: that is, that the most ultimate reality should not be identified with the many plural distinct things we typically observe and the distinctions between them. The ultimate is not dual or plural, and especially, at the ultimate level there is no distinction between subject and object. Yet all of that still doesn’t necessarily mean that the ultimate is one.