Scotistic realism (also Scotist realism or Scotist formalism) is the Scotist position on the problem of universals. It is a form of moderate realism, which is sometimes referred to as 'scholastic realism'. The position maintains that universals exist both in particular objects and as concepts in the mind. The "problem of universals" was an ancient problem in metaphysics about whether universals exist. For John Duns Scotus, a Franciscan philosopher, theologian and Catholic priest, universals such as "greenness" and "goodness" exist in reality. This is opposed to the later nominalism of William of Ockham, and the earlier conceptualism of Abelard, which say universals exist only within the mind and have no external or substantial reality, or universals don't exist at all (including the mind). In addition, Scotus doesn't think that universals exist in some "third realm" or "Platonic heaven", as Plato thought (i.e. Platonism). In this way, Scotistic realism can be seen as a middle ground between Aristotelian realism (i.e. immanent realism) and conceptualism. Scotistic realism can also be seen to take a nod to Platonism. Not because Scotus thinks that universals ultimately trace back to a "Platonic Heaven"; rather, because (for Scotus) universals ultimately trace back to ideas in God's mind. Therefore, scotistic realism affirms that universals exist in particular objects, finite minds, and the infinite mind of God. The problem of universals existed as early as Plato, who taught the Theory of Forms, that universal "forms" existed. This opinion was rejected by many later thinkers, such as Peter Abelard, who instead argued that forms are merely mental constructs. Scotus denied these claims; in his Opus Oxoniense he argued that universals have a real and substantial existence. For Scotus, the problem of universals was closely tied to that of individuation, by identifying what makes a particular thing this or that particular thing; we could also come to understand if any form of universal exists, it is in this work that Scotus introduces the word "haecceity", which means the "thisness" of a particular object – what makes it what it is.