C1.
C2.
R is a primary reason why an agent performed the action A under the description d only if R consists of a pro-attitude of the agent toward actions with a certain property, and a belief of the agent that A, under the description d, has that property. A primary reason for an action is its cause.
(Donald Davidson, 'Actions, Reasons and Causes', Journal of Philosophy LX, 1963) As Davidson notes, in practice reason-explanations typically mention only the attitude or the belief, not both: e.g., "He is shining his shoes because he believes it will impress the boss." As a first effort to elucidate the 'because' in such explanations, one might naturally offer the following. "He is doing A because he believes it is to do X" means:
C2a
He is doing A, he believes to do A is to do X, and, other things being equal, had he not believed that he would not have done A.
C2a seems a relatively unmysterious way to express one's contention that the agent's belief was what 'made the difference' between his doing A and not doing A. Additionally, it is a causal interpretation of 'He did A for reason X'. To say C caused E is to say that if C hadn't occurred, and everything else had been just as it was, E wouldn't have occurred.
According to C2a, to say someone did A because he believed that would be to do Xis to say that if he hadn't had this belief, he wouldn't have done A. So, C2a is also a natural way to take C2, the claim that reasons are causes.
According to Jack Meiland, 2 however, C2a quite misrepresents the logic of acting for reasons, and is vulnerable to counterexamples. I shall illustrate his claim with an example of my own. Meiland's view is simply that it might be true of someone who did A for reason X that he would have done it for another reason, had he not believed to do A was to do X.