<<Would it be at all accurate to describe an illocutionary act as "cause", and a perlocutionary one as "effect"?

Off the cuff, at least one notable difference might be that the perlocutionary is an interpretive condition established by the illocutionary act wherein *either an action or non-action would function as the cognate of the effect in a cause and effect relationship. The very fact that non-action is then specified as *a **determinate non-action would be a definitive part of that condition. The occurrence or non-occurrence of the requested action, then, would not be the effect, the space in which that occurrence might be interpreted--which space is opened as a requirement of the illocutionary--might, however, be considered as the effect of the illocutionary. We would be talking, then, of cause and effect in the realm of the interpretation of speech acts. But that's just a guess.