  Aristotle, as interpreted by medieval commentators, had gone on to say that concepts were similitudes or signs of things, and this raised the question of what is meant by ‘thing’. In other words, what is it that we understand when an utterance such as ‘man’ or ‘animal’ establishes an understanding? The usual assumption from Boethius at least until the end of the thirteenth century was that the understanding is of some kind of universal, an essence or common nature, and when logicians asked whether spoken words primarily signified concepts or things, the issue was whether concepts or common natures should be taken as the primary significates of an utterance. If the concept was said to be the primary significate, then the common nature was the secondary significate. If the common nature was said to be the primary significate, then individuals having that nature were often said to be the secondary significates.  The issue was complicated by various views about the nature of concepts as opposed to intelligible species, and about the status of common natures, and their precise relation to individuals, but fortunately these details do not concern us here. So long as common natures in some sense played a role in the signification of common nouns, there was a strong temptation to speak as if there are individual natures which play a similar role in the signification of singular terms. From Boethius on, there are many references to individual forms, and such terms as Socrateity (Socrateitas) and Platonicity (Platonitas) were frequently used, even by Thomas Aquinas. On the other hand, the Aristotelian insistence, taken up by Aquinas in particular, that the intellect cannot grasp individuals as such made the explanation of how we can understand Socrates more complicated. There did not seem to be a concept of Socrateity that corresponded to the form spoken of. Moreover, the very notion of an individual nature seemed incompatible with Aristotelianism. As a result, some thinkers in the second half of the thirteenth century held that what the grammarian counts as a proper name is not properly a name, since it does not signify a common nature.