 The third source for doctrines of analogy is metaphysics. The first part of Aristotle’s Metaphysics had been translated by the mid-twelfth century, though the full text was recovered only gradually. One crucial text is found in Metaphysics 4.2 (1003a33–35): “There are many senses (multis modis) in which being (ens) can be said, but they are related to one central point (ad unum), one definite kind of thing, and are not equivocal. Everything which is healthy is related to health…. and everything which is medical to medicine….” In this text, Aristotle raises the general problem of the word ‘being’ and its different senses, and he also introduces what is known as pros hen equivocation or focal meaning, the idea that different senses may be unified through a relationship to one central sense. Another foundational text is from Avicenna’s Metaphysics, also translated into Latin during the twelfth century, where he writes that being (ens) is neither a genus nor a predicate predicated equally of all its subordinates, but rather a notion (intentio) in which they agree according to the prior and the posterior. As we shall see below, this reference to the prior and the posterior is particularly important.