 The increase or decrease of a moral quality is either an effect of the impact of the opposite quality (or a change in the degree of intensity of the same quality), or else the result of human external acts. For example, frequent generous actions lead to an increase of generosity. Performing morally good actions intensifies the virtues, whereas the constant practice of evil diminishes them. Virtues and vices can be described in terms of different degrees of intensity, so one can say that a man can be more or less generous during his lifetime. And just like physical qualities, Kilvington states that the intensity of a moral quality has only an extrinsic limit, so that one cannot perfect one’s virtue infinitely.