Editing Problem of universals (section)

===Medieval realism===
{{main|Medieval realism}}
Boethius mostly stayed close to Aristotle in his thinking about universals. Realism's biggest proponents in the Middle Ages, however, came to be [[Thomas Aquinas]] and [[Duns Scotus]]. Aquinas argued that both the essence of a thing and its existence were clearly distinct;<ref>On Being and Essence, Ch I.</ref> in this regard he is also Aristotelian.

Duns Scotus argues that in a thing there is no real distinction between the essence and the existence; instead, there is only a [[formal distinction]].<ref>Opus Oxoniense I iii 1-2</ref> Scotus believed that universals exist only inside the things that they exemplify, and that they "contract" with the [[haecceity]] of the thing to create the individual. As a result of his realist position, he argued strongly against both nominalism and conceptualism, arguing instead for [[Scotist realism]], a medieval response to the [[conceptualism]] of [[Peter Abelard|Abelard]]. That is to say, Scotus believed that such properties as 'redness' and 'roundness' exist in reality and are mind-independent entities.

Furthermore, Duns Scotus wrote about this problem in his own commentary (''Quaestiones'') on Porphyry's ''Isagoge'', as Boethius had done. Scotus was interested in how the mind forms universals, and he believed this to be 'caused by the intellect'.<ref>{{cite book |last1=Scotus |first1=Duns |title=Quaestiones in librum Porphyrii Isagoge |pages=q. 4 proemium}}</ref> This intellect acts on the basis that the nature of, say, 'humanity' that is found in other humans and also that the quality is attributable to other individual humans.<ref>{{cite book |last=Noone |first=Timothy B. |editor-last=Williams |editor-first=Thomas |title=The Cambridge Companion to Duns Scotus |url=https://archive.org/details/cambridgecompani00will |url-access=limited |publisher=Cambridge University Press|date=2003 |pages=[https://archive.org/details/cambridgecompani00will/page/n117 100]–129 |chapter=Universals and Individuation |isbn=978-0-521-63563-9}}</ref>