Book IX Chapter 2

Since some such originative sources are present in soulless things, and others in things possessed¹ of soul, and in soul, and in the rational part of the soul, clearly some potencies² will, be non-rational and some will be non-rational and some will be accompanied by a rational formula. This is why all arts, i.e. all productive forms of knowledge, are potencies; they are originative sources of change in another thing or in the artist himself considered as other.

And each of those which are accompanied by a rational formula is alike capable of contrary effects, but one non-rational power produces one effect; e.g. the hot is capable only of heating, but the medical art can produce both disease and health. The reason is that science is a rational formula, and the same rational formula explains a thing and its privation, only not in the same way; and in a sense it applies to both, but in a sense it applies rather to the positive fact. Therefore such sciences must deal with contraries, but with one in virtue³ of their own nature and with the other not in virtue of their nature; for the rational formula applies to one object in virtue of that object’s nature, and to the other, in a sense, accidentally. For it is by denial and removal that it exhibits the contrary; for the contrary is the primary privation, and this is the removal of the positive term. Now since contraries do not occur in the same thing, but science is a potency⁴ which depends on the possession of a rational formula, and the soul possesses an originative source of movement; therefore, while the wholesome⁵ produces only health and the calorific only heat and the frigorific only cold, the scientific man produces both the contrary effects. For the rational formula is one which applies to both, though not in the same way, and it is in a soul which possesses an originative source of movement; so that the soul will start both processes from the same originative source, having linked them up with the same thing. And so the things whose potency is according to a rational formula act contrariwise to the things whose potency is non-rational; for the products of the former are included under one originative source, the rational formula.

It is obvious also that the potency of merely doing a thing or having it done to one is implied in that of doing it or having it done well, but the latter is not always implied in the former: for he who does a thing well must also do it, but he who does it merely need not also do it well.

1 possessed   

adj.疯狂的；拥有的，占有的

参考例句：

• He flew out of the room like a man possessed.他像着了魔似地猛然冲出房门。
• He behaved like someone possessed.他行为举止像是魔怔了。

2 potencies   

n.威力( potency的名词复数 )；权力；效力；（男人的）性交能力

参考例句：

• The soft gelatin liquid filled capsule manufacturing process is the same for all proposed potencies. 软明胶液体填注胶囊的生产工艺对所有提出的效用是一样的。 来自互联网

3 virtue   

n.德行，美德；贞操；优点；功效，效力

参考例句：

• He was considered to be a paragon of virtue.他被认为是品德尽善尽美的典范。
• You need to decorate your mind with virtue.你应该用德行美化心灵。

4 potency   

n. 效力，潜能

参考例句：

• Alcohol increases the drug's potency.酒精能增加这种毒品的效力。
• Sunscreen can lose its potency if left over winter in the bathroom cabinet.如果把防晒霜在盥洗室的壁橱里放一个冬天，就有可能失效。

5 wholesome   

adj.适合；卫生的；有益健康的；显示身心健康的

参考例句：

• In actual fact the things I like doing are mostly wholesome.实际上我喜欢做的事大都是有助于增进身体健康的。
• It is not wholesome to eat without washing your hands.不洗手吃饭是不卫生的。