I. The Definition and Essence of Original Depravity
"Original sin is the guilt of the whole human race, on account of the fall of our first parents. It consists in a want of the knowledge of God and of his will in the mind, and of an inclination to obey God with the heart and will; in the place of which there is an inclination to those things which the law of God forbids, and an aversion to those things which it commands, resulting from the fall of our first parents, Adam and Eve, and from them made to pass over into all their posterity, thus corrupting our whole nature, so that all, on account of this depravity, are subject to the eternal wrath of God; nor can we do anything pleasing to him, unless forgiveness be obtained for the sake of the Son of God, our Mediator, and the Holy Ghost renew our nature."
"Original sin comprehends, therefore, these two things: exposure to eternal condemnation on account of the fall of our first parents, and a depravity of our entire nature since the fall." [Zacharias Ursinus - Commentary on the Heidelberg]
"Original sin, then, may be defined a hereditary corruption and depravity of our nature, extending to all the parts of the soul, which first makes us obnoxious to the wrath of God, and then produces in us works which in Scripture are termed works of the flesh." [John Calvin - Institutes]
"The sinfulness of that estate whereinto man fell, consists in the guilt of Adam's first sin, the want of original righteousness,and the corruption of his whole nature, which is commonly called original sin, together with all actual transgressions which proceed from it." [Thomas Vincent - The Shorter Catechism]
II. The Loss of Original Righteousness (The Privative Element)
"The same thing is expressed, although somewhat more obscurely, in the common definition of original sin which is generally attributed to Anselm: "Original sin is a want of original righteousness which ought to be in us." Original righteousness was not only a conformity of our nature with the law of God, but it also included divine acceptance and approbation. In the place of this conformity with the divine law, we now have depravity; and in the place of this approbation, we have the displeasure of God, which has followed in consequence of the fall."
"That we are also, even from the moment of our birth, destitute of righteousness, and have inclinations contrary to the law of God." [Zacharias Ursinus - Commentary on the Heidelberg]
"...original sin was not only a privatio but that in it there was at the same time a total corruption of human nature." [Herman Bavinck - Reformed Dogmatics]
"The want of original righteousness doth include-- 1. Want of true spiritual knowledge in the mind. 2. Want of inclination and power to do good; and want of all spiritual affections in the will and heart." [Thomas Vincent - The Shorter Catechism]
"Adam made us all bankrupts. In innocence Adam had a stock of original righteousness to begin the world with, he could give God personal and perfect obedience; but, by his sin, he was quite broken, and beggared all his posterity. We have nothing to pay; all our duties are mixed with sin, and so we cannot pay God in current coin." [Thomas Watson - The Lord's Prayer]
III. The Deep Corruption of the Soul and Body
"This want of righteousness, which is comprehended in sin, includes, as it respects the mind, ignorance and doubt with regard to God and his will; and as it respects the heart, it includes a want of love to God and our neighbor, a want of delight in God and an ardent desire and purpose to obey all his commandments; together with an omission of such actions as the law of God requires from us."
"Disordered inclinations consist in a stubbornness of the heart, and an unwillingness to comply with the law of God, and the judgment of the mind, as it respects actions which are proper and improper; together with a depravity and propensity of nature to do those things which God forbids, which evil is called concupiscence." [Zacharias Ursinus - Commentary on the Heidelberg]
"For our nature is not only utterly devoid of goodness, but so prolific in all kinds of evil, that it can never be idle. Those who term it concupiscence use a word not very inappropriate, provided it were added, (this, however, many will by no means concede,) that everything which is in man, from the intellect to the will, from the soul even to the flesh, is defiled and pervaded with this concupiscence; or, to express it more briefly, that the whole man is in himself nothing else than concupiscence." [John Calvin - Institutes]
"...his spirit is proud, erring, defiled and therefore must be broken, enlightened, cleansed... his conscience is stained and needs cleansing; his desire, inclination and will extend to what is forbidden and are powerless for good; and the body, with all its members... stands in the service of unrighteousness. In one word, sin does not adhere to and around but in the human being and spreads over the whole human being and over all humanity..." [Herman Bavinck - Reformed Dogmatics]
"The contagion of his sin at once spread through the entire man, leaving no part of his nature untouched, but vitiating every power and faculty of body and soul. This utter corruption of man is clearly taught in Scripture, Gen. 6:5; Ps. 14:3; Rom. 7:18." [Louis Berkhof - Systematic Theology]
IV. Total Inability and Spiritual Death
"The nature of man in its corrupt state since the fall, is entirely unable to fulfill what the law demands; yea, it cannot so much as commence acceptable obedience to God..." "The Scriptures clearly teach these two things, that the wisdom of the flesh cannot be subject to the law of God, and that all those who are not subject thereto, stand exposed to the curse of the law." [Zacharias Ursinus - Commentary on the Heidelberg]
"There is none righteous no, not one: there is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that does good, no, not one. Their throat is an open sepulchre; with their tongues they have used deceit; the poison of asps is under their lips: Whose mouth is full of cursing and bitterness: their feet are swift to shed blood: destruction and misery are in their ways: and the way of peace have they not known: there is no fear of God before their eyes..." [John Calvin - Institutes]
"By total depravity, is not meant that all men are equally wicked; nor that any man is as thoroughly corrupt as it is possible for a man to be; nor that men are destitute of all moral virtues. All this is perfectly consistent with the Scriptural doctrine of total depravity, which includes the entire absence of holiness; the want of due apprehensions of the divine perfections, and of our relation to God as our Creator, Preserver, Benefactor, Governor, and Redeemer. There is common to all men a total alienation of the soul from God so that no unrenewed man either understands or seeks after God; no such man ever makes God his portion, or God's glory the end of his being. The apostasy from God is total or complete. All men worship and serve the creature rather than, and more than the Creator. They are all therefore declared in Scripture to be spiritually dead. They are destitute of any principle of spiritual life." [Charles Hodge - Systematic Theology]
"Positively, it does indicate: (1) that the inherent corruption extends to every part of man’s nature, to all the faculties and powers of both soul and body; and (2) that there is no spiritual good, that is, good in relation to God, in the sinner at all, but only perversion." [Louis Berkhof - Systematic Theology]
V. Original Sin as the Source of All Actual Transgressions
"The effects of the first sin are: 1. Exposure to death, and the privation and destruction of the image of God in our first parents. 2. Original sin in their posterity, which includes exposures to eternal death, and a depravity and aversion of our whole nature to God. 3. All actual sins, which proceed from original sin; for that which is the cause of a cause, is also the cause of the effect. The first sin is the cause of original sin, and this of actual sins."
"An evil root, or principle, such as the fall of our first parents, brings forth of itself, a corrupt and rotten branch, corresponding with its own nature, which satan now also by his fraud and lies, cultivates just as plants; but it is all in vain that he should so labor, if we do not offer ourselves to him to be moulded according to his will." [Zacharias Ursinus - Commentary on the Heidelberg]
"For although they have not yet produced the fruits of their own unrighteousness, they have the seed implanted in them. Nay, their whole nature is, as it were, a seed-bed of sin, and therefore cannot but be odious and abominable to God." [John Calvin - Institutes]
"Why do men break forth into actual sins—but because they do not mortify heart sins? Suppress the first risings of pride, lust, and passion. Original sin unmortified, will prove such a root of bitterness as will bring forth the cursed root of scandalous sin!" [Thomas Watson - The Lord's Prayer]
VI. The Legal Imputation and Righteous Transmission of Guilt
"Original sin is neither transmitted through the body, nor through the soul, but through the transgression of our first parents; on account of which, God, even whilst he creates the soul, at the same time deprives it of original righteousness, and such other gifts as he conferred upon our first parents upon the condition that they should transmit them to, or lose them for, their posterity, according as they themselves should retain or lose them."
"The cause, therefore, of the first sin, or of the fall of our first parents in Paradise, was the devil tempting and urging man to sin: and the will of man freely separating itself from God, and falling in with the suggestions of the tempter. This fall of Adam is the efficient cause of original sin both in himself and in his posterity." [Zacharias Ursinus - Commentary on the Heidelberg]
"Man, since he was corrupted by the fall, sins not forced or unwilling, but voluntarily, by a most forward bias of the mind; not by violent compulsion, or external force, but by the movement of his own passion; and yet such is the depravity of his nature, that he cannot move and act except in the direction of evil." [John Calvin - Institutes]
"Humanity is a massa perditionis. Sin is above all pride, superbia in the soul and concupiscentia is the body. Sin has been in Adam the deed of us all and therefore has become the lot of us all. It is carentia dei, privatio boni, not only an act but a condition, natura vitiata, a defectus, inopia, corruptio, a non posse non peccare." [Herman Bavinck - Reformed Dogmatics]