According to Wikipedia Materialism “holds that the only thing that exists is matter; that all things are composed of material and all phenomena (including consciousness) are the result of material interactions. In other words, matter is the only substance.”
Materialism is, whether or not you know it, the philosophy at the heart of (and laying the foundation for) the theory of Evolution. Evolution, you see begins with the a priori assumption that there is no God – no deity – no supernatural anything. The only thing that is real is matter (and energy) and everything that is can be explained by the properties of it. If it can’t be explained without God, then it can’t be real. Your soul, your mind, your thoughts, dreams, ideas and memories are simply the result of the physical interactions of physical matter (eg. in your brain).
It seems to me that there are two reasons why one should think this is a bunch of silliness. Number one. If all thought, is simply a process of material interactions then there can be no right or wrong thought. To call one kind of material interaction (with its attendant result) wrong cannot apply. It simply is. Therefore there would be no reason to disagree with anything anyone ever thought – including the thought that there must be not only a spiritual component to life, but a supernatural spiritual being responsible for creating and sustaining all that matter. Yet see how accepting materialists are of any such idea (produced, as they would say only by material interactions). Obviously they can still think that there are some things which are more real than others.
The second reason materialism does not, and cannot, amount to much is stated very well by C.S. Lewis, who identified this problematic philosophy so many decades ago:
If the solar system was brought about by an accidental collision, the the appearance of organic life on this planet was also an accident, and the whole evolution of Man was an accident too. If so, then all our present thoughts are mere accidents – the accidental by-product of the movement of atoms. And this holds true for the thoughts of the materialists and astronomers as well as for anyone else’s. But if their thoughts – i.e. of materialism and astronomy – are merely accidental by-products, why should we believe them to be true? I see no reason for believing that one accident should be able to give a correct account of all the other accidents. It’s like expecting that the accidental shape taken by the splash when you upset a milk jug should give you a correct account of how the jug was made and why it was upset.
Two accidents, no matter how great they are, just don’t make a truth. If there is no outside guiding force or principle (eg a spiritual reality) behind all thought then every thought is simply random chance of randomly interacting particles of matter. But random chance cannot be taken for truth. Again, it just is. So what makes materialistic random material interactions more “true” than the material interactions leading to a trust in God?
Just because matter “is” it does not follow that nothing else can be. Just because we can’t measure something directly doesn’t disprove its existence. (Ask astronomers about Dark Energy and Dark Matter, or an archeologist about “deep” time!) Nor does being able to study the physical stuff of my brain tell you what my inner-most thoughts are. But that’s fine, because now you know!