Unbelief the refusing assent to testimony, the withholding of due belief. According to Kant, it is the withholding of assent to that which, though objectively insufficient as a ground of cognition, is subjectively sufficient as a ground of faith. Moral unbelief is the rejection of that which, though we cannot know it, is yet morally necessary, as faith in God, freedom, and immortality. "It includes," says Dr. Guyse, "disaffection to God, disregard to his word, prejudices against the Redeemer, readiness to give credit to any other than him, inordinate love to the world, and preferring of the applause of men to the "approbation of God." "Unbelief," says Charnock, "is the greatest sin, as it is the foundation of all sin; it was Adam's first sin; it is a sin against the Gospel, against the highest testimony; a refusal to accept of Christ upon the terms of thee Gospel. It strikes peculiarly at God; is the greatest reproach of him, robs him of his glory, is a contradiction to his will, and a contempt of his authority." The causes of unbelief are Satan, ignorance, pride, and sensuality. The danger of it is great; it hardens the heart, fills with presumption, creates impatience, deceives with error, and finally exposes to condemnation (Joh 3:11).
Naturalistic unbelief is that which is indifferent and opposed to revelation. The unbelief of reason is the making our reason independent of its own needs the renunciation of the faith of reason. See Charnock, Works, 2, 601; Case, Sermons, ser. 2; Porteus, Sermons, vol. 1, ser. 2; Owen, Reasons of Faith; Hannam, Compendium, 2, 26; Churchill, Essay on Unbelief; Buck, Theol. Dict. s.v.; Fleming and Irauth, Vocab. of Phil. Sciences, s.v.