It is proposed in this Essay to consider the reasons for and against believing in the truth of Christianity, meaning by that term, as will be explained later on (Chapter XIII.), the doctrines contained in the Three Creeds. For convenience the subject has been divided into three Parts, Natural Religion, the Jewish Religion, and the Christian Religion; but the second of these may be omitted by anyone not specially interested in that subject. At present we are considering _Natural Religion_ only, which deals with the great questions of the Existence of God, and the probability, or otherwise, of His making some Revelation to man. And we will commence at the very beginning, though the first chapter will unfortunately have to be rather technical. (_A._) THE ORIGIN OF THE UNIVERSE. Now by the universe is meant the _material_ universe, which includes everything that exists (earth, sun, stars, and all they contain), with the exception of immaterial or spiritual beings, if there are any such. And by this universe having had an _origin_ is meant that it was at some time acted on by a _Free_ Force, that is to say, by a force which does not always act the same under the same circumstances, but which can act or not as it pleases. No doubt such a force would be totally different from all the known forces of nature; but there is no difficulty in understanding what is meant by the term, since man himself _seems_ to possess such a force in his own free will. He _seems_ for instance to be able to raise his hand, or not, as he likes. We are not, of course, assuming that man's will is really free, but merely that the idea of a free force, able to act or not as it pleases, is well known and generally understood. Hence the statement that the universe had an origin means that at some time or other it was acted on by such a Free Force; in other words, it has not existed for ever under the fixed and invariable forces of nature, and without any external interference. We have now to consider the two arguments in favour of this, which may be called the Philosophical and the Scientific argument. (1.) _The Philosophical Argument._