Things are spoken of in a twofold way as being potential and actual. For we say that the child at the breast is a potential scholar, for he is so equipped that, if taught, he will become a scholar. Further, we speak of a potential and an actual scholar, meaning that the latter is versed in letters, while the former has the power of interpreting letters, but does not put it into actual use: again, when we speak of an actual scholar, we mean that he puts his power into actual use, that is to say, that he really interprets writings.