Monism:
https://en.wikipedia.org/wiki/Monism
Monism attributes oneness or singleness (Greek: μόνος) to a concept e.g., existence. Various kinds of monism can be distinguished:
Priority monism states that all existing things go back to a source that is distinct from them e.g., in Neoplatonism everything is derived from The One.[1] In this view only one thing is ontologically basic or prior to everything else.
Existence monism posits that, strictly speaking, there exists only a single thing, the Universe, which can only be artificially and arbitrarily divided into many things.[2]
Substance monism asserts that a variety of existing things can be explained in terms of a single reality or substance.[3] Substance monism posits that only one kind of stuff exists, although many things may be made up of this stuff, e.g., matter or mind.