Different types of monism include:

Substance monism, "the view that the apparent plurality of substances is due to different states or appearances of a single substance"

Attributive monism, "the view that whatever the number of substances, they are of a single ultimate kind"

Epistemological monism, where "ultimately, everything that can be thought, observed and engaged, shares one conceptual system of interaction, however complex."

Partial monism, "within a given realm of being (however many there may be) there is only one substance"

Existence monism, "the view that there is only one concrete object token (The One, "Τὸ Ἕν" or the Monad)"

Priority monism, "the whole is prior to its parts" or "the world has parts, but the parts are dependent fragments of an integrated whole"

Property monism, "the view that all properties are of a single type (e.g., only physical properties exist)"

Genus monism, "the doctrine that there is a highest category; e.g., being"

Views contrasting with monism are:

Metaphysical dualism, which asserts that there are two ultimately irreconcilable substances or realities such as Good and Evil, for example, Gnosticism and Manichaeism.

Metaphysical pluralism, which asserts three or more fundamental substances or realities.

Metaphysical nihilism, negates any of the above categories (substances, properties, concrete objects, etc.).

Monism in modern philosophy of mind can be divided into three broad categories:

Idealist, mentalistic monism, which holds that only mind or spirit exists.

Neutral monism, which holds that one sort of thing fundamentally exists, to which both the mental and the physical can be reduced

Material monism (also called Physicalism and materialism), which holds that the material world is primary, and consciousness arises through the interaction with the material world

Eliminative Materialism, according to which everything is physical and mental things do not exist

Reductive physicalism, according to which mental things do exist and are a kind of physical thing

Arguments

Isn't what caused monism to exist plural from it, making it invalid

This statement is only made in the language of pluralism, not by the language of monism.
The axioms of monism are not violated by this argument.

Left-click: follow link, Right-click: select node, Scroll: zoom