 Some further background for the development of doctrines of analogy is provided by Aristotle’s discussion of scientific reasoning in his Posterior Analytics, first commented on in the 1220s by Robert Grosseteste. One important issue was how analogical relations might be used to find a way of referring to things which did not belong to one genus and lacked a common name. A popular example throughout the middle ages involved Aristotle’s account of the relation between the ‘bone’ of a cuttlefish, a spine, and a normal bone (Posterior Analytics, 14.2, 98a20–23), though there was some disagreement about the type of analogy involved. Even more important was Aristotle’s view that scientific reasoning requires demonstrative syllogisms, which, in order to be logically valid, must have a middle term that avoids the fallacy of equivocation. How far analogical terms could fill that role was a frequent topic of discussion and controversy. In the thirteenth century, in his questions on Aristotle’s Physics, Geoffrey of Aspall remarked that analogy did not rule out univocity or prevent a subject from being one, while in the early fourteenth century, Scotus preferred to preserve unity by abandoning the use of analogical terms. In the late fifteenth century Cajetan strongly supported the claim that analogical terms could function as middle terms. None of these authors suggested that natural science and theology could appeal to analogical relationships to produce probabilistic rather than demonstrative arguments.