_The Mercersburg Review_ denies the demonstrative force of the evidences of natural religion and positive revelation; referring us to conscience, or the moral sense, as the ground of belief in God and in Jesus Christ. This is another proof of the truth of our judgment, that the radical intellectual disease which Protestantism has produced requires treatment by a thorough dosing with sound philosophy. The corruption of theology has brought on a corruption of philosophy, and heresy has produced scepticism, so that we can hardly find a sound spot to begin with as a _point d'appui_ for the reconstruction of rational and orthodox belief. We do not despise the argument from conscience and the moral sense, or deny its validity. We did not specially draw it out, because we were not writing a complete treatise on natural theology; but it is contained in the metaphysical argument establishing the first and final cause. Apart from that, it has no conclusive force. What is conscience? Nothing but a practical judgment respecting that which ought to be done or left undone. What is the moral sense, but an intimate apprehension of the relation of the voluntary acts of an intelligent and free agent to a final cause? It is only intellect which can take cognizance of a rule or principle directing a certain act to be done or omitted, or of the intrinsic necessity of directing all acts toward a final cause or ultimate end. The intellect cannot do this, or deduce an argument from conscience and the moral sense for the existence of God, unless it has certain infallible principles given it in its creation; and with these principles, the existence of God and all natural theology can be proved by a metaphysical demonstration, proceeding from which, as a basis, we prove Christianity and the Catholic Church by a moral demonstration which is reducible to principles of metaphysical certitude. Deny this, and conscience, or the moral sense, is a mere feeling, a sensible emotion, a habit induced by education, a subjective state, which is just as available in support of Buddhism or Mohammedanism as of Christianity. _The Mercersburg Review_ is trying to sustain itself midway down the declivity of a slippery hill, afraid to descend where the mangled remains of Feuerbach lie bleaching in the sun, and unwilling to catch the rope which the Catholic Church throws to it, and ascend to the height from whence Luther, in his pride and folly, slid. Kant's miserable expedient of practical reason may suit those who are content with such an insecure position; but it will never satisfy those who look for true science, and certain, infallible faith.