Sec. 9. We have first the argument drawn from the existence of the human mind. This is an argument which, for at least the last three centuries, and especially during the present one, has been more relied upon than any other by philosophical thinkers. It consists in the reflection that the being of our own subjective intelligence is the most certain fact which our experience supplies, that this fact demands an adequate cause for its explanation, and that the only adequate cause of our intelligence must be some other intelligence. Granting the existence of a conditioned intelligence (and no one could reasonably suppose his own intelligence to be otherwise), and the existence of an unconditioned intelligence becomes a logical necessity, unless we deny either the validity of the principle that every effect must have an adequate cause, or else that the only adequate cause of Mind is Mind. It has been a great satisfaction to me to find that my examination of this argument--an examination which was undertaken and completed several months before Mr. Mill's essay appeared--has been minutely corroborated by that of our great logician. I mention this circumstance here, as on previous occasions, not for the petty motive of vindicating my own originality, but because in matters of this kind the accuracy of the reasoning employed, and therefore the logical validity of the conclusions attained, are guaranteed in the best possible manner, if the trains of thought have been independently pursued by different minds. Sec. 10. Seeing that, among the advocates of this argument, Locke went so far as to maintain that by it alone he could render the existence of a Deity as certain as any mathematical demonstration, it is only fair, preparatory to our examining this argument, to present it in the words of this great thinker. He says:--"There was a time when there was no knowing (_i.e._, conscious) being, and when knowledge began to be; or else there has been also a knowing being from all eternity. If it be said, there was a time when no being had any knowledge, when that eternal being was void of all understanding, I reply, that then it was impossible there should ever have been any knowledge: it being as impossible that things wholly void of knowledge, and operating blindly, and without perception, should produce a knowing being, as it is impossible that a triangle should make itself three angles bigger than two right ones. For it is as repugnant to the idea of senseless matter, that it should put into itself, sense, perception, and knowledge, as it is repugnant to the idea of a triangle, that it should put into itself greater angles than two right ones."[4]