 Although there is sometimes a correlation between reasons why, on the one hand, and evidentiary relations, on the other, few generalisations about this can be safely made. If A is a reason why B has occurred (and so perhaps also is evidence that B has occurred), then the occurrence of B will sometimes be a reason for thinking—but not a guarantee—that A has occurred. If A is no more than a reason for thinking that B has occurred, then B will sometimes be a reason why—but not a guarantee that—A has occurred. Going back to example (i) above, my opening the door (without violence) was a reason for thinking, that is to say evidence, that I had used the key. That I used the key, however, was not just a reason for thinking that I had opened the door, but one of the reasons why I was able to open the door. What is important is that the “if” clause of a conditional may do any of three things described in the present section. One of these is well captured by classical truth-functional logic, namely (i) introduce a sentence from which the consequent follows in the way modelled by an operator such as hook. But there are two other jobs that “if” may do as well, namely: (ii) state a reason why what is stated in the consequent is the case; (iii) state a reason for thinking that what is stated in the consequent is the case even when this is not a reason why.