Then remembering that many of Descartes’ works had, owing to the opposition of the Romish Church, never been printed, I decided to find out at once whether by any chance this might be one of them. I sent immediately to Paris for a complete edition of Descartes, which had recently been published, and soon found that this volume was not among them. A little further inquiry satisfied me of the authenticity of the MS., and that it was entirely unknown. "You may remember that Descartes, in his ’Discourse on Method,’ published in 1637, says, ’It appears to me that I have discovered many truths more useful and more important than all I had before learned, or even expected to learn. I have essayed to expound the chief of these discoveries in a treatise which certain considerations prevent me from publishing.’ Now we know that the chief consideration was his fear of offending the Church, and every one who has read Descartes’ published works must observe through them a perpetual veiling of what he thought to be true so as to avoid being brought in conflict with the religious opinions of his day. Notice this passage from the work just mentioned. ’It may be believed without discredit to the miracle of creation, that things purely material might in course of time have become such as we observe them at present, and their end is much more easily conceived when they are beheld coming in this manner gradually into existence, than when they are only considered as produced at once in a finished and perfect state.’ "He then applies this theory to man. He says that as yet he has not sufficient knowledge to treat of this development, and is obliged to remain satisfied with the supposition that God formed the body of man wholly like to one of ours, but at first placed in it no rational soul. Having gone thus far and apparently fearing to go further, he breaks off suddenly and never satisfactorily returns to the subject in his published works. But how different is his method when we turn to the manuscript before me, which I fancy must have been his last work, as it is unfinished! How much more lucid and complete we find his conclusions here! There is no attempt to suppress his real view. I will give you briefly a summary of the chief conclusions which interested me, and which will be enough for the present purpose. "’All things have slowly developed.’ "’Man is the most perfectly developed being of whose existence we are conscious.’ "’The lower orders of life have a varying number of powers of perception which we term senses.’ "’The higher orders of life have five.’ "’These senses diminish in power as they increase in number, being relieved one by the other.’ "’No deterioration in sense-power is known to have taken place without causing deterioration to the possessor unless at the same time accompanied by the development of a new perceptive faculty.’