1. Cause must always precede effect.
2. You cannot be conscious of a thought before you think it.
3. Therefore, you cannot consciously cause thoughts.
The logic seems infallible. However, it is intensely counterintuitive. It seems like common sense to say, "I consciously create my thoughts."
It may be that I'm missing the point (I haven't had my daily ration of chocolate yet), but what's wrong with this way of looking at it? Conscious or not, a thought can't be its own cause -- at least, not given our usual assumptions. That's what I take your premise 1 to entail. And it seems right: I can't be conscious of a particular thought X before I think it. (It may be, for all that, that I can think it before I'm conscious of it.) But why can't my conscious thought X be the cause of a later conscious thought Y ? For example, my thinking now about a jigger of gin might cause me to think, a moment later, that there's a bottle of gin in the freezer. Or maybe the issue is this: if I'm going to consciously cause a thought about Vienna, the content of that thought must already be part of the thought that does the causing. In that case, I'm conscious of the thought before I've thought it, contrary to premise 2. But then premise 2 ends up suspect, doesn't it? Couldn't I be sitting here...