Plotinos · Plotinus
FORM IS NOT A QUALITY; BUT A REASON.
Is form a quality? No: form is a reason. Now what is constituted by (material) substance, and reason? (In the warm body) it is neither what burns, nor what is visible; it is quality. If, however, it be said that combustion is an act emanating from reason, that being hot and white are actualities, we could not find anything to explain quality. QUALITIES ARE ACTS OF BEING, PROCEEDING FROM REASONS AND ESSENTIAL POTENTIALITIES. What we call a complement of being should not be termed a quality, because they are actualizations of being, actualizations which proceed from the reasons and the essential potentialities. Qualities are therefore something outside of being; something which does not at times seem to be, and at other times does not seem not to be qualities; something which adds to being something that is not necessary; for example, virtues and vices, ugliness and beauty, health, and individual resemblance. Though triangle, and tetragon, each considered by itself, are not qualities; yet being "transformed into triangular appearance" is a quality; it is not therefore triangularity, but triangular formation, which is a quality. The same could be said of the arts and professions. Consequently, quality is a disposition, either adventitious or original, in already existing beings. Without it, however, being would exist just as much. It might be said that quality is either mutable or immutable; for it forms two kinds, according to whether it be permanent or changeable.
Text from Project Gutenberg, public domain in the United States.