Plotinus

“ By this analogy, warmth, as a concomitant of the specific nature of fire, may very well be no quality in fire but an Idea-Form belonging to it, one of its activities, while being merely a Quality in other things than fire: as it is manifested in any warm object, it is not a mode of Reality but merely a trace, a shadow, an image, something that has gone forth from its own Reality- where it was an Act- and in the warm object is a quality. ”

“ Such completions of a Reality cannot be called qualities since they are its Acts emanating from the Reason-Principles and from the essential powers. A quality is something persistently outside Reality; it cannot appear as Reality in one place after having figured in another as quality; its function is to bring in the something more after the Reality is established, such additions as virtue, vice, ugliness, beauty, health, a certain shape. ”

“ Quality is a condition superadded to a Reality whose existence does not depend upon it, whether this something more be a later acquirement or an accompaniment from the first; it is something in whose absence the Reality would still be complete. It will sometimes come and go, sometimes be inextricably attached, so that there are two forms of Quality, the moveable and the fixed.
3 The Whiteness, therefore, in a human being is, clearly, to be classed not as a quality but as an activity- the act of a power which can make white ”

“ But the Archetypes of all such qualities, the foundation in which they exist primarily, these are Activities of the Intellectual Beings.
And; one and the same thing cannot be both Quality and non-quality: the thing void of Real-Existence is Quality; but the thing accompanying Reality is either Form or Activity: there is no longer self-identity when, from having its being in itself, anything comes to be in something else with a fall from its standing as Form and Activity. ”

“ In the swan the whiteness is not constitutive since a swan need not be white: it is constitutive in ceruse, just as warmth is constitutive of the Reality, fire.
No doubt we may be told that the Reality in fire is [not warmth but] fieriness and in ceruse an analogous abstraction: yet the fact remains that in visible fire warmth or fieriness is constitutive and in the ceruse whiteness. ”

“ The Reality there- possessing Authentic Being in the strictest sense, with the least admixture- is Reality by existing among the differentiations of the Authentic Being; or, better, Reality is affirmed in the sense that with the existence of the Supreme is included its Act so that Reality seems to be a perfectionment of the Authentic Being, though in the truth it is a diminution ”