It will be seen from this statement that Dr. Mivart regards his opponents as having laid the basis of their systems on the quicksands of the most radical scepticism; for certainly, if the fact of a το ἐγω be called in question, all knowledge must go by the board, its containing subject being no better than a myth. Those casting a doubt upon the truth of this proposition are by themselves happily styled Agnostics, or know-nothings, and Dr. Mivart includes in the category such distinguished names as Hamilton, Mansel, Mill, Lewes, Spencer, Huxley, and Bain. These writers, one and all, have repeatedly asserted the relativity of our knowledge――_i.e._, its merely phenomenal character. They do not deny that we possess knowledge, but that we can predicate nothing as to its absolute truth. They claim, indeed, themselves to have sounded the whole diapason of human knowledge, but they regard it only as a mirage which appears real to the eye whilst beholding it, but is none the less a mirage in itself. Dr. Mivart tersely points out the absurdity of this principle of the agnostic philosophy by stating that either this knowledge is absolute――_i.e._, objectively valid――or has no corresponding reality outside of the mind, in which case it represents nothing――_i.e._, is no knowledge at all. Those, then, who insist upon the relativity of all knowledge are “in the position of a man who saws across the branch of a tree on which he actually sits, at a point between himself and the trunk.” For if our knowledge be purely relative, we know it but relatively, and that relative knowledge of it is in turn relative, and so on _ad infinitum_. In other words, if we assert of our knowledge that it is relative――_i.e._, purely subjective――we affirm an objective fact; for however much the facts of the mind be subjective in relation to the objects represented, they become objective in regard to the mind viewing them as the term point of knowledge; so that to affirm of _all_ knowledge that it is purely relative is equal to affirming that the knowledge we have of that knowledge is not the knowledge thereof, but a similar modification of the mind having no business to look for anything beyond itself. This surely is a _reductio ad absurdum_; yet such threads and thrums are made the warp and woof of so-called scientific philosophy.