I believe that there is nothing even close to non-trivial certainty in philosophy, at least outside of ethics and psychology. For this reason, I believe in monism at about 60%. Furthermore, I believe that materialism is much more preferable to idealism, at about 60%. I think this may mean I believe in materialism at about 36%. Am I a materialist?
Let's calculate: 36% of materialism and 40% of them of idealism = 14,4%, so 50,4% of materialism or idealism, but stop... what is 49,6%?
You definitely at most part 49,6% Dark-Materialist!
I would suggest to frame this as a betting exercise, not a probability; probabilities are facts about frequencies in large sample sets, and there's only the one reality to be monistic or not.
Suppose these percentages are the ratios at which you'd consider it a good bet if God came down from heaven and offered you odds before divinely revealing the true nature of reality beyond all possible doubt.
your prior bets are well considered
you are confident that you have considered all possible answers
you are confident in your assessments that the prior bets are indeed necessary conditions for the secondary bets
...then it is rational to convert the odds on the prior bets to fractions of the whole (so e.g. 6:4 odds becomes 6/(6+4) = 0.6) and multiply the odds to obtain the ratio at which a secondary bet is also a good bet.
1 is subjective. 3 looks good in this case, materialism is a kind of monism.
However, you should not be confident in 2: idealism and materialism don't form a complete set of ways that reality can be monistic. See also panpsychism ("all is spirit") and pantheism ("all is God/gods"), and possibly others that I haven't considered. What if your assessed weightings are panpsychism 70, pantheism 20, materialism 6, idealism 4? Then materialism is preferred to idealism by a 6:4 ratio, but your bet on materialism (after multiplying by 6/10 for monism) should be made at odds of only 36:964, or 3.6% of the total set of outcomes.
Be careful of over-estimating very small ratios when doing this with a large set of possibilities. Humans are bad at intuiting a difference between 1:100 and 1:100000, and there are plenty of things that aren't even worth a 1:100000 bet.
Hmmm. There are not very many actual materialists left among serious philosophers. The discoveries of modern physics in the last century, where energy, fields, and probability envelopes seem more fundamental than objects, pretty much killed materialism.
The plurality of philosophers today are physicalists, where “what we discover about the subjects studied by physics” takes the place of “matter” in a monist ontology. But there are a lot of problems with this worldview.
The first problem is that a field of study is intrinsically open, both to its content, and its completeness. Physics does not presume monism, nor the causal closure of physics. Hence “what physics learns” cannot be a monist stand in for materialism, without some other NON physics assumptions added. The best known articulation of this problem is Hempel’s Dilemma. The lack of a case for causal closure within physics itself supplements Hempel.
The second issue is the nature of logic and information. Many theoretical physicists are trending toward treating physics as reducible to math. The Copenhagen interpretation “shut up and calculate” basically does this, and the rationale for Everett, that “the other world are in the math therefore they exist” is explicitly reductive to math. Others treat it as reducible to information, which is what the holographic approaches to physics do. Both information and math are in the general category of abstractions, and reducing to them is a version of idealism. Few physicists embrace this full on idealism, but many admit that characterizing our universe requires specifying both objects and information about them. Which is a dualism. Information and math are driving physics in the direction of either a dualism or a monist idealism.
The third issue is the status of reductionism and emergence. Physicalism, to be a monism, requires everything to reduce to physics. But the near consensus today is that the other sciences do not reduce to physics. See section 5 of SEPs article on Scientific Reduction. The majority view is pluralism, that the other sciences, AND non science fields, study real things. And how they relate/interact with physics is TBD. Pluralism does not support a monism. Physicalists who embrace it hold by a strong version of emergence, but emergence principles are still unspecified, as is an epistemology that produces two classes of “real”. The “real real” of physics and the “dependent/emergent” real of all other fields. Popperian science only generates one class of real.
The fourth concern is the hard problem of consciousness. No physicalist theory explains consciousness. Apply Darwinian variance to them, and all would predict we should not be conscious, or have been falsified by test cases. A long term “problem” like this (over 150 years for HPC) is generally seen by those who don’t hold by the view that faces the “problem” as a definitive refutation. Consider the similar “problem of evil”. Non theists consider it a definitive refutation of an omniGod.
You realize that philosophy is complex. An ontological worldview, tied to an epistemological theory, is therefore unlikely to be a slam dunk that one can spell out in complete and convincing terms.
I suspect that once you investigate the points I summarized, you will abandon the materialist label for physicalism, but that due to the four subsequent problems noted, you are only going to consider yourself “physicalist leaning”.
Four three good books by sympathetic but now formerly physicalist leaning philosophers, see Daniel Stoljar’s Physicalism, Jaegwon Kim’s Physicalism or Something Near Enough, and Susan Blackmore’s A Very Short Introduction to Consciousness. I have reviews of all three on Amazon. Blackmore is a Neutral Monist, Kim an epiphenomenalist dualist but just in relation to qualia, and Stoljar has abandoned ontology for just open minded Popperian empiricism.
Am I a materialist?
This question doesn't make sense within the context of your argument, and cannot be answered as such.
There are some answers here that illuminate the question, but I'm going to take a simple tack and criticize the question. If you state the assignment of a property in terms of probability, then to ask whether or not the property applies with certainty is a fallacy, because in the premises of the argument, the probabilities that you explicitly state presume that it is undecided whether or not the property applies. To review, your argument states:
P1 I'm 60% likely to be a monist.
P2 I'm 60% likely to be a materialist rather than an idealist.
P3 I believe I'm 36% likely to be a materialist.
The question, "Am I a materialist?" is fundamentally the wrong sort of question to ask, because all three premises are probabilistic. Unless the numbers come out to 0% or 100% when using frequentist notions of probability (though your usage is subjective, not frequentist), one cannot claim certainty in a conclusion. Your numbers do not come out to 0% or 100%, so it's a bad question. The well-formed question in this argument is instead "What is the probability I am a materialist?" And for the record, your belief (which is an additional premise because it's a propositional attitude) doesn't make it so but only offers to the reader the insight that you are using multiplication of probabilities as a frequentist does in calculations raising the philosophical question of whether such a technique is appropriate using subjective probabilities. I would, for example, be inclined that your use of numbers in this circumstance is an example of false precision:
False precision (also called overprecision, fake precision, misplaced precision and spurious precision) occurs when numerical data are presented in a manner that implies better precision than is justified; since precision is a limit to accuracy (in the ISO definition of accuracy), this often leads to overconfidence in the accuracy, named precision bias.
By what grounds do your premises use such numerical accuracy to begin with? If we strip out the false precision, we still have:
P1: It's likely I am a monist.
P2: It's likely I am materialist.
P3: I believe its unlikely I am a materialist.
What should the conclusion be drawn about being a materialist? Well, it seems that if you believe you think it's more likely you're a materialist than an idealist, and you believe you unlikely to be a materialist, then your conclusion is irrational and that your premises are therefore suspect to begin with.
If we suppose that much of philosophy has the same branching nature of materialism/physicalism and monism, and that it is the case that there is no near certain non-trivial knowledge to be had from it, then there seems to be two options
we can conclusively or near conclusively debunk a philosophy (100% sure that idealism is not true)
we don't believe our philosophical positions, just hold them as the most likely among their alternatives (36% physicalist and 24% idealist).
Both look a bit like negative meta-philosophies: philosophy works to exclude beliefs (at 100% or as less appealing than another).