This, in my judgment, is the ultimate issue of Descartes’ argument; but it is proper for me to point out that we have left Descartes himself some way behind us.  He stopped at the famous formula, “I think, therefore I am.”  But a little consideration will show this formula to be full of snares and verbal entanglements.  In the first place, the “therefore” has no business there.  The “I am” is assumed in the “I think,” which is simply another way of saying “I am thinking.”  And, in the second place, “I think” is not one simple proposition, but three distinct assertions rolled into one.  The first of these is, “something called I exists;” the second is, “something called thought exists;” and the third is, “the thought is the result of the action of the I.”

Now, it will be obvious to you, that the only one of these three propositions which can stand the Cartesian test of certainty is the second.  It cannot be doubted, for the very doubt is an existent thought.  But the first and third, whether true or not, may be doubted, and have been doubted.  For the assertor may be asked, How do you know that thought is not self-existent; or that a given thought is not the effect of its antecedent thought, or of some external power?  And a diversity of other questions, much more easily put than answered.  Descartes, determined as he was to strip off all the garments which the intellect weaves for itself, forgot this gossamer shirt of the “self;” to the great detriment, and indeed ruin, of his toilet when he began to clothe himself again.

But it is beside my purpose to dwell upon the minor peculiarities of the Cartesian philosophy.  All I wish to put clearly before your minds thus far, is that Descartes, having commenced by declaring doubt to be a duty, found certainty in consciousness alone; and that the necessary outcome of his views is what may properly be termed Idealism; namely, the doctrine that, whatever the universe may be, all we can know of it is the picture presented to us by consciousness.  This picture may be a true likeness—­though how this can be is inconceivable; or it may have no more resemblance to its cause than one of Bach’s fugues has to the person who is playing it; or than a piece of poetry has to the mouth and lips of a reciter.  It is enough for all the practical purposes of human existence if we find that our trust in the representations of consciousness is verified by results; and that, by their help, we are enabled “to walk surefootedly in this life.”

Thus the method, or path which leads to truth, indicated by Descartes, takes us straight to the Critical Idealism of his great successor Kant.  It is that Idealism which declares the ultimate fact of all knowledge to be a consciousness, or, in other words, a mental phenomenon; and therefore affirms the highest of all certainties, and indeed the only absolute certainty, to be the existence of mind.  But it is also that Idealism which refuses to make any assertions, either positive