  A second difference between the order of being (reality) and the order of signifying (language) is revealed by the process known as “contraction.” In the conceptual order, a thing is contracted from its genus to its species by a differentia that distinguishes the species from other kinds within a genus. For example, the genus “animal” is contracted to the species “man” by the differentia “rational,” thus setting human beings apart from other kinds of animals. In the order of reality, however, being is not contracted to any of the ten genera, because ‘being’ does not have the same meaning when applied to every category. The ten highest genera have nothing in common with each other other than the fact that they are called ‘being’ (Pini, 2005). However, insofar as the user of the term is concerned, ‘being’ can be contracted to one of the categories, for when one says ‘being in itself,’ one intends to signify substance, even though in the order of reality no such contraction occurs. This difference between reality and thought lies at the heart of Scotus' doubt concerning the possibility of deriving the number of categories.