'Philosophy is a Hunger of the Soul after Knowledge. What is Knowledge?--reduced through various intermediate stages to question, what is the common and essential quality in all knowledge--the quality which makes knowledge knowledge? Answer approached by raising question: What is the essential quality in all food--the quality which makes food food? This is obviously its physically nutritive quality. Whatever has the nutritive property is food; whatever has it not is not food, however like excellent beef and mutton it may be. So in regard to knowledge, its common and essential quality--the quality in virtue of which knowledge is knowledge--is its nutritive quality. Whatever nourishes and satisfies the mind is knowledge, as whatever nourishes and satisfies the body is food. The intellectually _nutritive property_ in knowledge is the common and essential property in knowledge. What is the nutritive quality in knowledge? Answer (without beating about the bush)--TRUTH. 'What is TRUTH? Answer--Truth is whatever is supported by Evidence. 'What is EVIDENCE? Evidence is whatever is supported by Experience. What is EXPERIENCE? Here we stop; we can only divide Experience into its kinds, which are two, _Experience of Fact_ and _Experience of Pure Reason_. Observe the manoeuvre in the last line by which you knaves of the anti-metaphysical school are outwitted. You _oppose Pure Reason_ to _Experience,_ and philosophers generally assent to the distinction. This at once gives your school the advantage, for the world will always cleave to experience in preference to anything else, leaving us metaphysicians, who are supposed to abandon experience, hanging as it were in baskets in the clouds. But _I_ do not abandon experience as the ultimate foundation of _all_ knowledge; only I maintain that there are _two_ kinds of experience, both of which are equally experience, the experience of Fact and the experience of Pure Reason. You are thus deprived of your advantage. I am as much a man of experience as you are.' Evidently it had been a question with Ferrier whether he should use the expression Experience, so well known to us now, or substitute for it Consciousness, which, as a matter of fact, he afterwards did: 'Why is it so grievous and fatal an error to confound Experience and Consciousness? Is not a man's experience the whole developed contents of his consciousness? I cannot see how this can be denied. And therefore, before you wrote, I was _swithering_ (and am so still) whether I should not make consciousness the basis of the whole superstructure--the raw material of the article which in its finished state is knowledge. After all, the dispute, I suspect, is mainly verbal.'