For example, Kant would prove the _a priori_ character and validity of the principle of causation by showing that without it science is impossible, that it helps “make experience.” Now, in terms, Hegel’s justification of this relation would be the same; he too would show that the fabric of experience implies and demands the causal relation. But in Kant’s case, the justification of the principle of causality by reference to the possibility of experience means that thought must continually inject this principle _into_ experience to keep it from disappearing: that experience must be constantly braced and reinforced by the synthetic action of thought or it will collapse. In short, the need of experience for this principle of causation means its need for a certain support outside itself. But Hegel’s demonstration of the validity of the causal principle is simply pointing out that the whole supports the part, while the part helps make the whole. That is to say, Hegel’s reference is not to some outside action of thought in maintaining fact as an object of knowledge; it is to the entire structure of fact itself. His contention is simply that the structure of fact itself, of the subject-matter of knowledge, is such that in one of its phases it presents necessarily the aspect of causality. And if this word “necessarily” gives pause, it must be remembered what the source of this necessity is. It does _not_ lie in the principle of causation _per se_; it lies in the whole fact, the whole subject-matter of knowledge. It is the same sort of necessity as when we say that a complete man _must_ have an eye; i. e., it is the nature of the human organism to develop and sustain this organ, while the organ, in turn, contributes to and thus helps constitute the organism. It is then evident that the question upon which the “refutation” of Hegel turns is not in showing that formal “thought” cannot give birth to truth except through the fructifying touch of experience. The question is simply whether fact—the subject-matter of knowledge—is such as Hegel presents it. Is it, in general, a connected system as he holds it to be? And, if a system, does it, in particular, present such phases (such relations, categories) as Hegel shows forth? These are objective questions pure and simple; questions identical, in kind, with the question whether the constitution of glucose is what some chemist claims to have found it.