Christianity is not a theory, or a speculation, but a life. Not a philosophy of life, but life, and a living process. It has been eighteen hundred years in existence. The practical inquirer has his foot on the rock when he knows that whoever needs not a Redeemer is more than human. Remove from him the difficulties that perplex his belief in a crucified Saviour, convince him of the reality of sin, and then satisfy him as to the fact historically, and as to the truth spiritually, of a redemption therefrom by Christ. Do this for him, and there is little fear that he will let either logical quirks or metaphysical puzzles contravene the plain dictate of his commonsense, that the Sinless One that redeemed mankind from sin must have been more than man, and that He who brought light and immortality into the world could not in His own nature have been an inheritor of death and darkness. A moral evil is an evil that has its origin in a will. An evil common to all must have a ground common to all. Now, this evil ground cannot originate in the Divine will; it must, therefore, be referred to the will of man. And this evil ground we call original sin. It is a mystery--that is, a fact which we see, but cannot explain; and the doctrine a truth which we apprehend, but can neither comprehend nor communicate. The article on original sin is binding on the Christian only as showing the antecedent ground and occasion of Christianity, which is the edifice raised on this ground. The two great moments of the Christian religion are, original sin and redemption; _that_ the ground, _this_ the superstructure of our faith. Christianity and redemption are equivalent terms. The agent and personal cause of the redemption of mankind is--the co-eternal word and only begotten Son of the living God. The causation act is--a spiritual and transcendent mystery, "that passeth all understanding." The effect caused is--the being born anew, as before in the flesh to the world, so now born in the spirit to Christ. Now, albeit the causative act is a transcendent mystery, the fact, or actual truth, of it having been assured to us by revelation, it is not impossible, by steadfast meditation on the idea and supernatural character of a personal will, for a mind spiritually disciplined to satisfy itself that the redemptive act supposes an agent who can at once act on the will as an exciting cause, and in the will, as the condition of its potential, and the ground of its actual, being.