I've probably read a hundred or so pages on my own, and 'recaps' by Russel, Durant, and have spoken with practicing philosophers about him. I have enough exposure that I've been able to make much more sense of why later philosophers seem obsessed about certain points that only make sense if you consider the historical philosophical tradition from Plato. But hearing people talk about him, especially when they insist on his continued relevance, it makes me think either I'm missing something or they're faking something.
But then again, I'd answer the questions you mentioned in a way I feel that most philosophers would find to be 'missing the point'. For example:
> What is justice?
A concept useful for regulating human societies. It's based on ultimately arbitrary heuristics that are effective for satisfying an approximately maximum number of people.
> What is good?
A word we use to label a fundamental behavior in our brains: we use values as something like utility functions in optimization processes. Ultimately there are constraints placed on the values we're capable of selecting which are imposed on us by our evolved biology, but we do have a good amount of freedom, so by studying human nature we can figure out which values are the most effective for creating the sort of lives we're interested in.
> What is the best way to govern?
We don't know yet. There probably is no best. If there is, we'll probably find it algorithmically.
> What is true?
There is too much ambiguity here to really answer, so I'll just choose one interpretation and say: whatever it is, it's highly unlikely that human minds would be capable of 'understanding' it ('understanding' being a human faculty, and not likely something important to the nature of the universe).
> A word we use to label a fundamental behavior in our brains: we use values as something like utility functions in optimization processes.
That position limits the degree to which ethics can be objective. Suppose some other culture believes in doing things we believe to be gravely immoral. If our idea of good is just "a behaviour in our brains" or a "utility function" or a product of "evolved biology", well then theirs is too, so how can we say our moral views are objectively better than theirs? The ability to say that certain behaviour is immoral, in an objective and transcultural way, is threatened by your position; and I think that threat is a good reason to reject it.
> > Where does knowledge come from?
> Brains.
You seem to treat (some version of) materialism as if it were obviously true, but I don't think its truth is obvious.
I'm inclined toward idealism, and I don't believe there are any good reasons to believe that materialism is more likely to be true than idealism.
> and I don't believe there are any good reasons to believe that materialism is more likely to be true than idealism.
You poke someone in the brain (or drop some chemicals in there), their behavior changes. This is a pretty good reason for considering the brain to be the generator of our minds. And then on top of that, we now have another hundred years or so of experiments (via neuroscience and its antecedents) and theoretical models which allow us to accurately predict things about how the brain in fact behaves, and how people's larger scale behavior conforms to that.
But that's only a reply I give because you called me a materialist after my answer of 'Brain.' In fact I'm not a thoroughgoing materialist, but we have enough data at this point to confidently say values arise from brains.
> You poke someone in the brain (or drop some chemicals in there), their behavior changes.
An idealist can say: Physical objects, events, and processes, and the correlations between them, are all patterns in the experiences of minds. "Brain" is a pattern in the experiences of minds. "Poke someone in the brain" or "drop some chemicals in there" are also patterns in the experiences of minds, and so likewise is "their behaviour changes". The fact that the former is regularly correlated with the later is a yet further pattern in the experiences of minds. There is nothing here that cannot be explained by idealism.
> This is a pretty good reason for considering the brain to be the generator of our minds
A materialist explains these observations in terms of brains generating minds, whereas an idealist can explain them in terms of minds generating brains. Since both can explain the evidence in terms of their own theories, it is unclear how this could be a reason to prefer one theory to the other.
> Physical objects, events, and processes, and the correlations between them, are all patterns in the experiences of minds
But there is no evidence of such minds, right? We have no ideas about where or what they are, or actually anything anything at all about them?
> whereas an idealist can explain them in terms of minds generating brains
But the difference is that causality is moving in a particular direction in the example I gave about brains being poked or having chemicals added to them, where the mind is affected by such actions. However, it has never been demonstrated in the opposite direction: there is an absence of a brain somewhere, then a mind does something, then a brain manifests. If the causality there were actually bi-directional, then that sort of thing would be observed too.
Now I know that when you say 'mind' you are referring to something else, and I partly just give the above answer to show how misleading it is to use the same term for what you're talking about (which I assume is more like the 'mind' of a monistic panpsychism).
I can grant your assertion that there is a mind-like something underlying everything, it's the substrate through which all matter appears (including brains), and actually believe something a little like that myself—but it doesn't change the fact that at the end of the days we're left with the matter thus generated, and that it is governed by certain predictable rules, etc. So for spiritual purposes perhaps it makes sense go ahead and contemplate the mind-medium that is more fundamental than our physical reality; but for the purpose of understanding how our universe works, you want to engage the materialist perspective.
So I think we agree that at least for transcendent, truly fundamental matters, materialism is insufficient. I think where we disagree is about which sort of things are fundamental/transcendent or not: 'knowledge' is something that I believe to be totally mundane and amenable to scientific description (same with 'justice' and the best way of governing), whereas philosophers have a tendency to elevate it. It makes sense that they would elevate it because in the days of its original elevation it was as unapproachable and mysterious to them as anything—as say, the notion of an afterlife, is to us. But time has passed, science encroached on that territory, and a lot of philosophers need to catch up.
Well, I am a mind, and so I have direct evidence of the mind that I am.
I don't have direct evidence of the existence of other minds. But I do have indirect evidence of their existence. And I believe I am justified in believing in their existence.
> We have no ideas about where or what they are
Why must a mind have a where? Must entities have a spatial location in order to exist? (Anyway, my sense experiences are from a particular varying spatial vantage point, so maybe that vantage point is the present location of my mind.)
As to what a mind is – according to idealism, minds are fundamental/irreducible/basic concepts, which cannot be explained in terms of anything else. Hence, to ask for an idea about "what a mind is", if that question presumes minds can be explained in terms of something more basic, is a mistaken question. But, the very same point applies to materialism, with respect to whatever it proposes to be the most fundamental concepts of reality–particles or waves or forces or fields or strings or branes or whatnot – whatever physicists ultimately settle upon as most fundamental, materialists will accept as most fundamental.
> or actually anything anything at all about them?
Well, it seems we can say lots of things about minds. They have a succession of thoughts, feelings, beliefs, desires, memories, habits, character, sense experiences, consciousness, unconsciousness, dreams, hallucinations, etc. We can describe their contents in great detail.
> which I assume is more like the 'mind' of a monistic panpsychism
When I say "mind", I am not intending to use that word in some special sense fundamentally different from the everyday one. I am simply proposing that mind, in (more or less) the everyday sense of that term, is a basic/fundamental/foundational aspect of reality rather than a non-basic/non-fundamental/non-foundational one.
"Monism" is ambiguous between type monism and token monism. Idealism and materialism are of course both forms of type monism, compared to substance dualism which is a type dualism. But not all idealists are token monists. Some idealists do of course say that only one mind really exists, and the existence of multiple minds is some sort of illusion. But, it is possible to be an idealist and yet insist on the existence of a real plurality of minds. I favour that later view.
Idealism needn't involve panpsychism either. It is open to an idealist to say that humans have minds, and even some higher animals have minds, but at the same time deny that rocks and trees and planets and stars and bacteria and atoms do. I observe correlations between my inner experiences and my outward behaviour – when I feel sad I will cry – and so observing similar outward behaviour in other humans, and even in some animals, I believe I am justified in concluding that those same inner feelings exist for them, even though I can't directly observe them. But I observe no such outward behaviour in bacteria or plants or rocks or planets or stars or atoms, so I don't have the same justification to conclude that they have minds.
> but for the purpose of understanding how our universe works, you want to engage the materialist perspective
I don't agree. Materialism is not part of the natural sciences, it is a metaphysical interpretation of the natural sciences. One can adopt a different metaphysical interpretation of the natural sciences – such as an idealist one – and then carry out the practice of the natural sciences just as well as the person who adopts the materialist metaphysical interpretation can.
> 'knowledge' is something that I believe to be totally mundane and amenable to scientific description (same with 'justice' and the best way of governing), whereas philosophers have a tendency to elevate it
To go back to my earlier point – if ethics/morality is "totally mundane and amenable to scientific description", then it cannot truly be objective in a transcultural and transpersonal way. I believe I have a moral duty to promote the idea that certain acts – for example, state violence against LGBT people – are gravely and objectively wrong, in a way that transcends cultural differences and personal opinions. Adopting your view undermines my ability to fulfil that duty. (In principle, if there was compelling rational evidence that your view was true, I would be forced to concede that evidence as overriding that duty – but I don't believe any such compelling evidence actually exists.) Hence, I cannot adopt your view.
It's not about the answers, but about thinking deeply about these questions and questioning your own assumptions (and those of others).
I'd highly recommend taking an intro to philosophy course, or one on ancient philosophy, where you can read the Socratic dialogues and engage with them in a group setting, along with others who are encountering these for the first time.
When done well, if you're lucky enough to have a good teacher and be in a group of students who are willing to engage fully with the reading and talk about it in class, this can be an experience like no other.
I've already taken in intro philosophy class. Furthermore, I've been debating philosophical points with friends since I was a kid—and since I've grown up two of my good friends who I spent multiple years talking philosophy with were either presently in grad school for philosophy or had finished with it.
I see what you mean about doing philosophy in a group setting, but for what I'm interested in anyway, I'm not going to have a great time debating the above questions with an intro to philosophy class. A starting point for me to enjoy it would be that my interlocutors would need to be able to have some degree of understanding of the answers I gave above, what points might be in their favor, and what their limitations might be.
I can say no philosopher I've met personally would answer those questions like I did (though I think I've read some who would), so I'm still very curious to see why we choose different ways. But my guess is still just that they'd answer differently if they had more knowledge of cognitive science and other topics.
But then again, I'd answer the questions you mentioned in a way I feel that most philosophers would find to be 'missing the point'. For example:
> What is justice?
A concept useful for regulating human societies. It's based on ultimately arbitrary heuristics that are effective for satisfying an approximately maximum number of people.
> What is good?
A word we use to label a fundamental behavior in our brains: we use values as something like utility functions in optimization processes. Ultimately there are constraints placed on the values we're capable of selecting which are imposed on us by our evolved biology, but we do have a good amount of freedom, so by studying human nature we can figure out which values are the most effective for creating the sort of lives we're interested in.
> What is the best way to govern?
We don't know yet. There probably is no best. If there is, we'll probably find it algorithmically.
> What is true?
There is too much ambiguity here to really answer, so I'll just choose one interpretation and say: whatever it is, it's highly unlikely that human minds would be capable of 'understanding' it ('understanding' being a human faculty, and not likely something important to the nature of the universe).
> Where does knowledge come from?
Brains.
> Why should any of this matter?
Because experience is real.