  This was a powerful objection. The standard reply to it is developed in John of Cornwall's Questions on the Posterior Analytics (1298-1300), and Walter Burleigh's Questions and Commentary on the Posterior Analytics (1300-10). John of Cornwall's work was at one time thought to be Scotus's, and it certainly seems to reflect Scotus's thinking on this point (Opus Oxoniensis I, Distinction 2, Question 2). The defense is to claim that there are two sorts of concepts possible of a substance, quidditative concepts, which are captured in the real definition, and concepts that express the quiddity only confusedly. Someone who does not know what the quiddity of a lion is nonetheless may have a concept of lion if he has encountered lions, but his concept is non-quidditative. To avoid begging the question in a demonstration of the highest sort, one must assert the quidditative concept of the non-quidditative concept of a substance. So, if one says that a lion (as commonly conceived) is in fact an animal with a certain genetic code, say, this is not a mere tautology, for the notion of the genetic code is not included in the everyday, non-quidditative concept of lion. Giles's reply is to the effect that the confused, simple concept of a substance possessed by the ordinary fellow in fact refers to the same reality as the real definition does, so that asserting the real definition of the confused concept simply asserts that the reality is itself, and so is a triviality, after all. This, of course, is not true of the definition of an attribute, since it obliquely refers to things other than the reality that is the attribute, namely its causes. So to discover the real definition of human and assert it of the simple, confused concept of human being is not to convey new information. To see the point of this reply, we must see that the standard way of identifying the real nature of a human being is simply to place it in its genus and identify its specific difference, but it is arguable that doing this in the case of a substance gives us no new information, but only places the thing in the right spot in a scheme of classification. It is a little hard to see how “a human being is a rational animal” does anything more than identify what we want to talk about. Of course, to say that this concrete thing is a rational animal is informative, but does it give us any different information than the assertion that this concrete thing is a human being? On the other hand, the causal definition of an attribute really does add to our information about it, as when we find that the noise-in-the-cloud, i.e. thunder, is a noise-in-the-cloud-produced-by-the-extinction-of-fire. These two notions are really distinct, for the one refers obliquely to fire, and the other does not.