This is just a note for record on what monism is (as opposed to dualism, Creation by a Supreme and maximally great and good being, etc). A useful point of departure is a diagram from Wikipedia on dualism (and they give only one type) vs monism:
Wikipedia notes, next to this:
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”
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, 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
Certain positions do not fit easily into the above categories, such as functionalism, anomalous monism, and reflexive monism. Moreover, they do not define the meaning of “real”.
That’s just to begin to grasp vocabulary. SEP gives an interesting exchange, if you are interested:
There are many monisms. What they share is that they attribute oneness. Where they differ is in what they attribute oneness to (the target), and how they count (the unit). So strictly speaking there is only monismrelative to a target and unit, where monism for target t counted by unit u is the view that t counted by u is one.
Monisms are correlative with pluralisms and nihilisms. Where the monist for target t counted by unit u holds that t counted by u is one, her pluralist counterpart holds that t counted by u is many, and her nihilist counterpart holds that t counted by u is none. Among pluralists it is sometimes useful to single out the dualist: the dualist for t and u holds that t counted by u is two
To illustrate these various doctrines for various targets and units, let the target t1= concrete objects, and let the unit u1= highest type. To be a monist for t1 counted by u1 is to hold that concrete objects fall under one highest type. The materialist, idealist, and neutral monist are all monists of this sort (substance monism). They all agree that concrete objects fall under one highest type, disagreeing only over whether the one highest type is material, mental, or something deeper.
To be a pluralist for t1 counted by u1 is to hold that concrete objects fall under more than one highest type. The Cartesian dualist is a pluralist of this sort (substance dualism). She holds that concrete objects fall under two highest types: the material (with the primary attribute of extension), and the mental (with the primary attribute of thought).
To be a nihilist for t1 counted by u1 is to hold that concrete objects fall under no highest type. The bundle theorist who is an eliminativist about concrete objects is a nihilist of this sort (substance nihilism). She rejects the target: she thinks that there are no concrete objects to count. One who accepts concrete objects but rejects the relevant notion of “highest” type would also be a nihilist for t1 counted by u1. She rejects the unit: she thinks that this is no way to count . . .
The relevant context is the challenge since Thales of Miletus:
ONE AND MANY CHALLENGE:
to account for unity and diversity in a coherent domain, reality, with room for responsible, rational, morally governed contingent creatures such as we are; on pain of collapse of credibility of our very rationality to think about such. Such self-defeat is a sign that a view is absurd.
The general challenge, in short is that of the one and the many. (NB: Thales proposed water as root substance.)
For record, I have argued for cause that, in describing core substances, materialist or physicalist monisms end in trying to account for the mind on a computational substrate. This ends in undermining rational freedom, putting in its place GIGO limited processing that is dynamic-stochastic.
For example, here is an adder circuit element for a computer ALU:
This is a key element for addition, exploiting how electronic circuits can implement boolean algebra thus the logic of bitwise addition.
Extending to a digital computer:
Extending into a Tanenbaum style stack model:
In short, a sophisticated electronic machine but not a free responsible, rational agent.
If you want to go analogue, here is a simple case, the sight for a classic 0.303 calibre SMLE Mk III:
Here, the curved ramp programs for bullet drop at various ranges, allowing for reasonably accurate fire. Again, a dynamic-stochastic system, not a rational free agent.
A neural network:
Here, cumulative weighted inputs trigger firing of neurons at nodes. Clever, but again a dynamic-stochastic system.
This is to remind us of Leibniz in his analogy of the mill:
It must be confessed, however, that perception, and that which depends upon it, are inexplicable by mechanical causes, that is to say, by figures and motions. Supposing that there were a machine whose structure produced thought, sensation, and perception, we could conceive of it as increased in size with the same proportions until one was able to enter into its interior, as he would into a mill. Now, on going into it he would find only pieces working upon one another, but never would he find anything to explain perception [i.e. abstract conception]. It is accordingly in the simple substance [–> the inherently unified monad], and not in the compound [–> composite made up from independently existing parts] nor in a machine [–> composite entity with function based on mechanical and/or stochastic interactions not insight, understanding, conceptualising, inferring based on meaning etc] that the perception is to be sought
Materialistic monism, reduction to matter, fails.
Mental type monisms, equally for cause, turn our first fact of conscious experience, embodiment and participation in a common world as living bodies, into a Plato’s cave type shadow show, a grand delusion. (I have suggested a thought test: cease breathing for an hour, in a dreamscape or vision or simulation, no consequences of significance; in waking reality, fatal consequences . . . this is strictly a don’t try this at home thought exercise. I recall a short Sci Fi novel where children raised in a simulation world identified base waking reality by the permanence of death there.)
I remember, to note.
In a simulation world by a super-intellect or hyper-computer, there are no experiences for the characters. If we try a network of nodes that each run sims of some sort, and are somehow self aware projecting embodiment in a world, such is clearly a network of Plato’s cave delusions, leading to the level two challenge. That is, the level two world of alleged self awareness of being a node may instead only be the next cave and so forth.
There is no good reason to doubt that our first facts of conscious reality are false. If we insist on the doubt, that leads to a regress of similar invited doubts at every successive level and one so enmeshed has no reason to take his or her rationality as perceived as credible. Think about extending this endlessly:
Or, we may ponder:
Would you buy a used car from a Cave-prisoner, or a brain in a vat?
While we’re at it let’s use the Smith model as a way to discuss a two-tier controller cybernetic loop that can model embodiment:
Of course, that does not mean that we do not err. We do, but there is no good reason to entertain wild hyperskeptical doubts that end in self-referential discredit of rationality.
It remains, that our worldviews face a need to address the challenge of the one and the many. Not easy, but it has been responsibly done.
This being a FYI that has room for illustrations, this will not further stretch out the threads taken up with such debates. The latest sidetracked thread is enough. END