There are explanations of different kinds that hold simultaneously. An explanation of the wrong kind (for example, evolutionary explanation) that is only similar (because of shared reasons) to the relevant explanation (of the right kind, in this case "goals", a normative or at least cognitive explanation) can be used to gain correct answers, used as a heuristic (evolutionary psychology has a bit of predictive power about human behavior and even goals). This further simplifies confusing them, so that instead of a rule of thumb, a source of knowledge, an explanation of the wrong kind would try taking a role that doesn't belong to it, becoming a definition of the thing being sought. For example, "maximizing inclusive fitness" can be believed to be an actual human goal.