  Following the standard medieval understanding of the opening lines of Aristotle's On Interpretation, Ockham holds that written and vocal words are conventional signs of mental concepts, which are in turn natural signs of things. To a certain extent, he also admits that written and vocal words correspond to mental concepts, so that, just as there are ten kinds of predication, i.e., ten kinds of vocal utterances (the ten categories), there are also ten kinds of concepts corresponding to them (see Panaccio 1999, 55).  However, Ockham argues that our natural experience gives us no reason to think that the terms we use for the categories signify ten extra-mental entities. Rather, experience supports the view that only individual substances and the accident of quality exist extramentally. Ockham uses many semantic devices to make his point (ibid., 71). For example, whereas Scotus might say that “Socrates is a father because of fatherhood,” Ockham would rather say that “Socrates is a father because he has generated a son” (Ockham 1991, V. q. 22, 472; Klima 1999, 136). In this way, instead of positing an abstract entity, viz., “fatherhood,” to account for why Socrates is a father, Ockham gives the activity of Socrates as an individual substance as the reason why Socrates is a father. However, in other contexts and for specifically theological reasons, particularly when it comes to the cases of the Trinity, the Incarnation, and the Eucharist, Ockham is willing to grant that relations are real. (see Adams 1987, 267, and Spade 1999, 104)