Matter & Materialism
I'm an unashamed materialist. Not in a dialectical mumbo jumbo Marxist sense, but more simply I think there's only one world, that reality is just as it is and has no 'meta' levels. So my faith, if you like, is only ever in the world itself, in matter. No supernatural or mystical supplement exists above and beyond matter.
People who like to think they are scientific tend to feel that this is their sort of materialism as well. They attack mysticism and any attempt to go beyond the facts of things. But nearly always they're not materialists at all. Because lurking away there unexamined is a rigid idealism, a splitting of reality into matter and 'representations' (thoughts, theories, equations etc.) of this matter. Most of what is called the scientific world view is this idealism, where you have the world and then you have this supplement that represents it, more or less truthfully, whether it be you perceiving it more or less accurately in your brain, or your theory is more or less 'true' to how things are.
For the average modern scientific person, matter is some stuff that just is what it is, and we can get to know what it consists of more or less accurately through studying it. So matter is a static underlying stuff, made up of electrons, protons, atoms in general etc. Most of us who've had a modern education in science are taught this, and really it's not that far removed from Newton's clockwork universe from several hundred years ago, where existence is just the interactions of these fundamental bits and pieces of matter. So if you knew where all of these bits and pieces were at any given time, you could explain everything in reality, including the near future.
This sort of materialism is one of the foundations of what we call the modern world. It's synonymous with what we tend to call 'reality'. It's where we get this idea that we have a capital-R Reality, which is the world as it is, unchanging and known more or less well (but supposedly better all the time) with our different scientific ways of interrogating it. The exact parallel with all of the religious traditions of the past and present who claim some more fundamental reality than the one we all live every day, which only some select priesthood can access via their various ritutals and instruments, is not very often seen.
The problem with this traditional materialism, which again is our modern religion, is that it has no idea about matter. Matter is not some underlying stuff, it's an always-changing stuff. Anybody who has worked with any sort of material knows that it always changes, depending what you do with it, and even if you do nothing it will change over time. It will corrode, tarnish and exhibit all sorts of properties, all by itself, all the time. As the old philosophers used to say, nature is a flux, it isn't a thing. You never step in the same river twice. Of course you could say "yes, but underneath all of that are those atoms which don't change, that's what matter is, in its essence". But atoms do change, all the time. Particles even pop in and out of existence once you get down to the sub-atomic scale, all by themselves and with no predictability.
You can't represent the world, you can only re-present it. That difference is profound. Our usual ideas about knowledge (what's technically called epistemology) exercise themselves with understanding how knowledge relates to the world. But a true materialist knows that it doesn't relate to or correspond with or represent the world, it's just some other part of the world, of matter. Epistemology is a myth, it's a field that shouldn't even exist. If I draw a picture of something, have I represented it in the sense of somehow accessing its deeper, underlying reality? No, I've just re-presented the object, in a new way, using paper and pencil. I've taken various characteristics of the object I'm drawing and folded them into the medium I'm re-presenting it with. There will be a link between my drawing and the object, but it's not a relationship of levels, where the representation exists in some other world, of truth or falsity. The link is all at the same level - that bit of the object there is re-presented with this line here, and that bit by this line here, etc.
Similarly if I use one of Newton's equations to calculate the acceleration of a brick dropped off a tower, have I shifted from the world into some metaphysical realm where I'm now dealing with the 'truth' of the world? Not at all, those equations are fully linked to the original world of the brick via the various instruments and calculation tools I use to determine the speed and acceleration. Try to 'apply' any theory without doing all of the practical work of setting up instruments which link or re-present the phenomenon and the equation.
That doesn't mean there is no such thing as knowledge. It's the relational thing again, it only means that knowledge is the expression of a set of relationships between things. It's not 'about' anything. If I chat to a person, then the words we exchange don't let me access the person as they 'really are' underneath all of those words, they set up a new relationship between me and them, via the medium of words. (And the words change both me and them, even if only subtly, as we exchange them, and we change the words too.) That lump of stuff which is the other person would respond differently if I used touch instead of words, or sang to them, or tried to bash them with a bit of 4x2 - I would get a different response with every different thing I did. I won't ever arrive at THE person, these things I'm doing don't all point to some single, underlying essence. Every lump of stuff is a set of always-changing relations, and every attempt I make to know it alters it yet again, setting up even more relations.
This is all Einstein meant when he forced physicists to go back to the drawing board and take into account simple things like clocks and rulers in what they did. That's what 'relativity' meant, that you couldn't understand instruments as pointing to some reality, they helped to constitute the reality they proposed to study.
Leaving high falutin' science aside, this applies to you as a human being too. You are all just 'stuff'. There is no you up in your brain, separate to your brain, lording it over yourself and staring out at the world. The brain is just another lump of matter. Similarly you don't represent the world to yourself via your perceptions, perceptions are stuff to. They're physical things. This doesn't reduce you to your biology, as the traditional materialism would have you believe with its split between stuff and representations of stuff. Because stuff isn't just static lumps, matter is relational, always-changing and therefore alive. Every atom of it.