Holy Scripture is very explicit in describing the effects of original corruption on the intellect and will of man. With respect to the intellect, original sin implies a total want of spiritual light, so that man by nature cannot know or understand the truths of God's Word which pertain to his conversion and salvation. Indeed, he is so blinded that he regards the Gospel as foolishness, 1 Cor. 2, 14, while he looks upon the very Law which condemns him, Gal. 3, 10-12, as the true way to salvation, Gal. 3, 1-3; Eph. 4, 17. 18. This dense spiritual darkness is not removed by education or culture, 1 Cor. 2, 6-9; Col. 2, 8, but solely by the Holy Ghost through the Gospel, Acts 16, 14; 2 Cor. 4, 6. While the intellect of corrupt man is unable to know the Gospel and is thus at fault negatively, it positively is prone to pass rash and false judgments concerning spiritual things, Acts 2, 13; 17, 18. 32, and to harden itself against the divine truth, Acts 7, 51.
The Formula of Concord describes this deplorable state of natural man as follows: "By the fall of our first parents man was so corrupted that in divine things pertaining to our conversion and the salvation of our souls he is by nature blind, so that, when the Word of God is preached, he neither does nor can understand it, but regards it as foolishness; also, that he does not of himself -draw nigh to God, but is and remains an enemy of God until he is converted, becomes a believer (is endowed with faith), is regenerated and renewed, by the power of the Holy Ghost through the Word when preached and heard, out of pure grace, without any cooperation of his own." Thor. Decl., II, 5.
Again: "Although man's reason or natural intellect indeed has still a dim spark of the knowledge that there is a God, as also of the doctrine of the Law, Rom. 1, 19 ff., yet it is so ignorant, blind, and perverted that, when even the most ingenious and learned men upon earth read or hear the Gospel of the Son of God and the promise of eternal salvation, they cannot from their own powers perceive, apprehend, understand, or believe and regard it as true, but the more diligence and earnestness they employ, wishing to comprehend these spiritual things with their reason, the less they understand or believe, and before they become enlightened and are taught by the Holy Ghost, they regard all this only as foolishness or fictions, 1 Cor. 2, 14; 1, 21; Eph. 4, 17ff.; Matt. 13, ll ff.; Luke 8, 18; Rom. 3, 11. 12. Accordingly the Scriptures flatly call natural man in spiritual and divine things darkness, Eph. 5, 8; Acts 26, 18; John 1, 5. Likewise the Scriptures teach that man in sins is not only weak and sick, but defunct and entirely dead, Eph. 2, 1. 5; Col. 2, 13." (Thor. Decl., II, 9. 10.)
With respect to the will of fallen man Holy Scripture teaches a) that it actually and constantly opposes the divine Law, Eph. 2, 3; 1 Pet. 4, 3. 4, and b) that on account of its total corruption it cannot but oppose God's will. Rom. 8, 7: "It is not subject to the Law of God, neither indeed can be." The will of natural man is therefore both in constant opposition to God and in constant agreement with Satan and his evil will, Rom. 8, 7 ; Eph. 2, 1 ; John 8, 44; Rom. 6, 17. 20; Heb. 2, 15. Even the externally good deeds of natural man (iustitia civilis) do not flow from true love of God, Eph. 2, 12, but at best from natural sympathy or compassion and similar causes, though generally such "good works" have their source in vainglory and work-righteousness, Matt. 23, 25-28.
The Augsburg Confession rightly declares (Art. II): "Since the fall of Adam all men begotten in the natural way are born with sin, that is, without the fear of God, without trust in God, and with concupiscence." And the Formula of Concord says: "In spiritual and divine things the intellect, heart, and will of the unregenerate man are utterly unable by their own natural powers to understand, believe, accept, think, will, begin, effect, do, work, or concur in working, anything; but they are entirely dead to what is good, and corrupt, so that in man's nature since the Fall, before regeneration, there is not the least spark of spiritual power remaining nor present by which of himself he can prepare himself for God's grace, or accept the offered grace, nor be capable of it for and of himself, or apply or accommodate himself thereto, or by his own powers be able of himself, as of himself, to aid, do, work, or concur in working, anything towards his conversion either wholly or half or in any, even the least or most inconsiderable, part, but that he is the servant (and slave) of sin, John 8, 34, and a captive of the devil, by whom he is moved, Eph. 2, 2; 2 Tim. 2, 26. Hence the natural free will according to its perverted disposition and nature is strong and active only with respect to what is displeasing and contra.ry to God." Thor. Decl., II, 7.
As the will of natural man is opposed to God, so also his appetition (appetitus sensitivus), which, prompted by inordinate desires, impels him to rush into all manner of vices that seem agreeable to his perverted senses, although these are prohibited by the divine Law, Rom. 1, 32; 1, 26-27; 13, 13. Original sin is therefore "the root and fountainhead of all actual sins," as the Formula of Concord rightly states Thor. Decl., I, 5.
It is this constant opposition to the divine will and habitual inclination to evil (habitualis inclinatio ad malum) that makes original sin a positive evil, or sin in the full sense of the term, indeed, the "chief sin" (principium et caput omnium peccatorum). The Augsburg Confession declares Art. II: "This disease, or vice of origin, is truly sin, even now condemning, and bringing eternal death upon, those not born again through Baptism and the Holy Ghost. They condemn the Pelagians and others Semi-Pelagianism, Scholasticism who deny that original depravity is sin and who, to obscure the glory of Christ's merit and benefits, argue that man can be justified before God by his own strength and reason."