This is a great point which materialists forget, that because they claim that all there is is what is observable, not being able to observe something is a disproof of the theory. There can be no doubt that the mind has control over the body. My typing this is proof of it. I am putting my thoughts by directing my fingers to move and type this. That the opposite may also be true, does not mean that this is not true also.
But what I am typing is not random words, but specific words which more or less are in accord with the grammar of the English language. My thoughts are in the English language and I think in English. However, a Frenchman will think in French and readily use French grammar in his thoughts. Greeks will do the same as well as those speaking many other languages will think in their own language. Now what quality of matter would allow for this? Words are just symbols, letters also are symbols. But these symbols are the way we think and these symbols are different in every language and the ordering of these symbols (the grammar) is also different in every language.
So what possible material explanation could be found for this? Are we to believe that we inherit the ability to understand and use these symbols from our parents? That cannot be since an adopted Chinese child will understand English as well as one whose parents spoke English. Another explanation which might be offered is that the symbols are somehow translated back and forth to a 'natural' base. However, how could matter alone accomplish a translation? Clearly translation has no materialistic basis either so that there is something within us which is beyond the material cannot be doubted.
Excellent points, gore3000. Drat those pesky "psychic phenomena."