We must acknowledge that the reasons which produce these things (as
heat, and whiteness) are beings, if taken in their totality; but on
considering their production, we see that what constitutes a whatness
or quiddity (the Aristotelian "what it were to be") in the intelligible
world, becomes a quality in the sense-world. Consequently, we always
err on the subject of the quiddity, when we try to determine it,
mistaking the simple quality for it (as thought Plato),[332] for, when
we perceive a quality, the fire is not what we call fire, but a being.
As to the things which arrest our gaze, we should distinguish them from
the quiddity, and define them by the qualities of sense (objects); for
they do not constitute the being, but the affections of being.