  Following Aristotle in De anima III.4, Aquinas argues, that the mind or the intellective part of the soul has no nature or rather it is nothing before it thinks of something. The active intellect abstracts the intelligible species from the sensitive species in the internal senses and places it in the potential intellect. Aquinas is here very close to the view we saw Avicenna defend above. The species actualizes the potential intellect as a form actualizes a potency. The intelligible species in the potential intellect constitutes the thought. The intellect is immaterial, according to Aquinas, and since he also famously thinks that matter is the principle of individuation, the intelligible species in the potential intellect is not individual, but universal. This is why Aquinas holds that a thought is always universal. 