Sec. 1. Few subjects have occupied so much attention among speculative thinkers as that which relates to the being of God. Notwithstanding, however, the great amount that has been written on this subject, I am not aware that any one has successfully endeavoured to approach it, on all its various sides, from the ground of pure reason alone, and thus to fix, as nearly as possible, the exact position which, in pure reason, this subject ought to occupy. Perhaps it will be thought that an exception to this statement ought to be made in favour of John Stuart Mill's posthumous essay on Theism; but from my great respect for this author, I should rather be inclined to regard that essay as a criticism on illogical arguments, than as a _careful_ or _matured_ attempt to formulate the strictly rational _status_ of the question in all its bearings. Nevertheless, as this essay is in some respects the most scientific, just, and cogent, which has yet appeared on the subject of which it treats, and as anything which came from the pen of that great and accurate thinker is deserving of the most serious attention, I shall carefully consider his views throughout the course of the following pages. Seeing then that, with this partial exception, no competent writer has hitherto endeavoured once for all to settle the long-standing question as to the rational probability of Theism, I cannot but feel that any attempt, however imperfect, to do this, will be welcome to thinkers of every school--the more so in view of the fact that the prodigious rapidity which of late years has marked the advance both of physical and of speculative science, has afforded highly valuable data for assisting us towards a reasonable and, I think, a final decision as to the strictly logical standing of this important matter. However, be my attempt welcome or no, I feel that it is my obvious duty to publish the results which have been yielded by an honest and careful analysis. Sec. 2. I may most fitly begin this analysis by briefly disposing of such arguments in favour of Theism as are manifestly erroneous. And I do this the more willingly because, as these arguments are at the present time most in vogue, an exposure of their fallacies may perhaps deter our popular apologists of the future from drawing upon themselves the silent contempt of every reader whose intellect is not either prejudiced or imbecile. Sec. 3. A favourite piece of apologetic juggling is that of first demolishing Atheism, Pantheism, Materialism, &c., by successively calling upon them to explain the mystery of self-existence, and then tacitly assuming that the need of such an explanation is absent in the case of Theism--as though the attribute in question were more conceivable when posited in a Deity than when posited elsewhere.