Monism attributes oneness or singleness to a concept, such as to 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. In this view only the One 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.
• Substance monism asserts that a variety of existing things can be explained in terms of a single reality or substance. Substance monism posits that only one kind of substance exists, although many things may be made up of this substance, e.g., matter or mind.
• Dual-aspect monism is the view that the mental and the physical are two aspects of, or perspectives on, the same substance.
• Neutral monism believes the fundamental nature of reality to be neither mental nor physical; in other words it is "neutral".