The Question of Causation I think you are probably approaching this in a similar manner to me.
I think there is an issue of language use invovled in what we are saying. When I read philosophical arguments involving the issue of causation, they terms are always framed in a specific manner -- often highly abstracted -- so as to be almost non-appliable to daily human life. Such framing makes perfect sense when it comes to the hard sciences that do not involve biological messiness, but less so when we talk of subjective experience and individual acts.
What bothered me was a reading a while back regarding how a mental state causes me to move my arm. The author framed the mental act as effecting the muscles, yet this is obviously an arbitrary point in the chain of events, as we could instead say 'No! That is too far down the line. The mental act to physical act begins at the neuronal level where the muscles received the signal," and then someone else may say "Wait a minute! The mental to phsyical act happens in the Brain".
The phsyical reductionist argument obvious suffers and it seems that a kind of elimitivism makes more sense from a physicalist perspective.
As for Mental to Mental, my position is we cannot say anything about such as it does not realy exist other than by way of using physical sensory data to progress the thought (real or imagined) as in the case of believing it will rain or not.
My view is that when people talk of Mental to Mental causation they are really talking about some mental state (physical or otherwise depending on your philosophical perspective) connected to another mental state by physical states.
To use a loose ananlogy, as Gazzaniga talked about split brain patients showing that the hemisphere effectively communicated in the physical world through sensory perception completely unbeknowst to the subject of the brain. If you are familiar?