Whatever might be the origin of this doctrine, it was eagerly adopted by the Christians, who judged it very convenient to their system of religion, all the parts of which are founded on the marvellous, and which made it a crime to admit any truths agreeable to reason and common sense. Thus, without going back to the inventors of this inconceivable dogma, let us examine dispassionately what this opinion really is; let us endeavor to penetrate to the principles on which it is supported; let us adopt it, if we shall find it an idea conformable to reason; let us reject it, if it shall appear destitute of proof, and at variance with common sense, even though it had been received as an established truth in all antiquity, though it may have been adopted by many millions of mankind. Those who maintain the opinion of the soul's immortality, regard it--that is, the soul--as a being distinct from the body, as a substance, or essence, totally different from the corporeal frame, and they designate it by the name of _spirit_. If we ask them what a spirit is, they tell us it is not matter; and if we ask them what they understand by that which is not matter, which is the only thing of which we cannot form an idea, they tell us it is a spirit. In general, it is easy to see that men the most savage, as well as the most subtle thinkers, make use of the word _spirit_ to designate all the causes of which they cannot form clear notions; hence the word spirit hath been used to designate a being of which none can form any idea. Notwithstanding, the divines pretend that this unknown being, entirely different from the body, of a substance which has nothing conformable with itself, is, nevertheless, capable of setting the body in motion; and this, doubtless, is a mystery very inconceivable. We have noticed the alliance between this spiritual substance and the material body, whose functions it regulates. As the divines have supposed that matter could neither think, nor will, nor perceive, they have believed that it might conceive much better those operations attributed to a being of which they had ideas less clear than they can form of matter. In consequence, they have imagined many gratuitous suppositions to explain the union of the soul with the body. In fine, in the impossibility of overcoming the insurmountable barriers which oppose them, the priests have made man twofold, by supposing that he contains something distinct from himself; they have cut through all difficulties by saying that this union is a great mystery, which man cannot understand; and they have everlasting recourse to the omnipotence of God, to his supreme will, to the miracles which he has always wrought; and those last are never-failing, final resources, which the theologians reserve for every case wherein they can find no other mode of escaping gracefully from the argument of their adversaries.