In the past I have, on several occasions, attempted to show that materialism is a logical necessity. For example if we could establish that the physical world is casually closed, and that epiphenomenalism is inconsistent, then we must turn to materialism as the only consistent position. In a way this is a negative argument for materialism, since it is an attempt to show that the other possible positions are flawed, and that the only way to resolve the problems faced by them is to adopt some version of materialism. Another such negative argument is the argument from rationality, which states that positions other than materialism cannot be rationally argued for (in the sense of reasoned thought, not sanity). You can read versions of these arguments here and here.
I consider such negative arguments sufficient reason to be a materialist, but there is, in addition to these, a positive argument for materialism. By this I mean that there are some criteria that we want our theories about the mind to meet, and that materialism meets these criteria better than the other possibilities. Specifically we want our theories to explain, and thus predict, the mind.
Materialism attempts to explain, and predict, the mind by arguing that certain kinds of collections of physical properties are behind what we think of as the mental properties. This can function as an explanation of the mental properties because by knowing about the physical properties that underlie them we can know what is “really” going on. Ideally we would be able to say why some creatures are conscious and some aren’t by appealing to some physical features of their constitution. Likewise, we could explain our perceptions, thoughts, and experiences by describing how the physical facts are responsible for mental life as we know it. And of course if the mental is really the physical then we can make predictions about it too, since we can have no problem in making predictions about physical facts.
Dualism, in both its property and substance forms, can neither predict nor explain mental life. According to dualism even if the mental facts aren’t fundamental and un-analyzable they might as well be, since we have no way, except through our experience, to know about them. And this makes dualism a bad explanation of the mind. If you ask the dualist why animals are conscious and plants aren’t they can’t tell you (assuming they don’t appeal to some supernatural force, like god, to explain who has “souls” and who doesn’t, and I don’t think many would accept this as a good explanation). Similarly, they can’t tell you how or why thinking about dogs is different than thinking about cats, all the dualist can say is that one experiences the thoughts as different. And, despite the fact that we can make observations about our own mental life, dualism can’t hope to make predictions about the mental either. To make predictions requires the ability to formulate general laws (as in: thoughts of type X will be followed by type Y). But since the mental properties are basically un-analyzable it is hard to tell how we would be able to determine if a thought fell within one category or another. It is true that upon experiencing the thought we would know, but it is hard to piece together laws from such observations. We need to know what features of type X make type Y follow it, so that we can speculate as to why those features have that causal effect.
Of course we might feel that the predictability problem could be resolved by the right kind of epiphenomenalism, which states that for any physical state there is only one possible accompanying mental state, even though the mental properties are separate from the physical properties. And thus we might reason that since we can predict future physical states we could also determine the accompanying future mental states, and thus predicting them indirectly. Unfortunately there is a flaw with this plan, which is that epiphenomenalism doesn’t give us a way to determine which mental properties will be connected with which physical state. Perhaps our version of epiphenomenalism could borrow part of a materialist theory, and where the materialist says that certain physical configurations are certain mental properties the epiphenomenalist could say that they ensure that those mental properties accompany them. But the epiphenomenalist cannot really adopt the materialist’s theory and change the wording, because the epiphenomenalist doesn’t have a reason to think that the materialist theory they are adopting should work. Why should certain physical states give rise to certain mental ones? The epiphenomenalist cannot say, because they have added a gap to the materialist theory without a way to fill it, so even if they can make predictions they can’t say why those predictions are likely to be correct.
There are those who think that the mind cannot be understood. Certainly I can’t prove that it can be, but to say that understanding it is impossible without a very good reason seems like simply giving up. And if we are attempting to understand the mind then materialism certainly looks like the best way to go.