(429a19) Anaxagoras says that since everything is a possible object of thought, mind, in order to dominate (that is, to know) must be pure from all admixture; for the copresence of what is alien to its nature is a hindrance and a block: it follows that it can have no nature of its own, other than that of having a certain capacity. Thus that in the soul which is called thought is, before it thinks, not actually any real thing. For this reason it cannot be regarded as blended with the body: if so it would acquire some quality, e.g. warmth or cold: as it is, it has none. It was a good idea to call the soul 'the place of forms', though this description holds only of the thinking soul, and even this is the forms only potentially, not actually