Reason and rational power are abilities that are complete in themselves. They drive their own actions. They start moving on their own. But they always aim straight toward whatever goal lies ahead of them. They go toward what can actually be done, whether or not it was their original target. This is why such actions are called 'straight achievements' — because they follow the most direct path.
Reason, and rational power, are faculties which content themselves with themselves, and their own proper operations. And as for their first inclination and motion, that they take from themselves. But their progress is right to the end and object, which is in their way, as it were, and lieth just before them: that is, which is feasible and possible, whether it be that which at the first they proposed to themselves, or no. For which reason also such actions are termed κατορθώσεις, to intimate the directness of the way, by which they are achieved.