After explaining at considerable length what Being is not, Aristotle now proceeds to ascertain what it is. He tells us that just as all number _quâ_ number must be either odd or even, so all Being _quâ_ Being must have certain universal attributes. These he sets himself to discover. When Descartes long afterwards entered on a somewhat similar inquiry, he fell back on the facts of his own individual consciousness. Aristotle, on the contrary, appeals to the common consciousness of mankind as embodied in ordinary language. In how many senses do we say that a thing is? The first answer is contained in his famous Ten Categories.[239] These are not what some have supposed them to be, _summa genera_ of existence, but _summa genera_ of predication. In other words, they are not a classification of things, but of the information which it is possible to receive about a single thing, more especially about the richest and most concrete thing known to us—a human being. If we want to find out all about a thing we ask, What is it? Of what sort? How large? To what does it belong? Where and when can we find it? What does it do? What happens to it? And if the object of our investigations be a living thing, we may add, What are its habits and dispositions? The question has been raised, how Aristotle came to think of these ten particular categories, and a wonderful amount of rubbish has been written on the subject, while apparently no scholar could see what was staring him in the face all the time, that Aristotle got them by collecting all the simple forms of interrogation supplied by the Greek language,[240] and writing out their most general expressions. Having obtained his categories, Aristotle proceeds to mark off the first from the other nine. The subject or substance named in answer to the question, What is it? can exist without having any quality, size, and so forth predicated of it; but they cannot exist without it. Logically, they cannot be defined without telling _what_ they are; really they cannot be conceived without something not themselves in which they inhere. They are like the tail of a kite, giving greater conspicuousness and buoyancy to the body, but entirely dependent on it for support. What our philosopher fails to perceive is, that the dependence is reciprocal, that substance can no more be conceived without attributes than attributes without substance; or rather that substance, like all other categories, can be resolved into Relation.[241]