What is the natural state of humanity?
We believe humanity is fallen from righteousness and, apart from the grace of our Lord Jesus Christ, is destitute of holiness and inclined to evil.
Catechism for the Global Methodist Church, question 46
5And the LORD saw that the wickedness of man was great on the earth, and that every intention of the thoughts of his heart was only evil continually.
5Behold, I was brought forth in iniquity, and in sin my mother conceived me.
3This is evil in all that is done under the sun, that one accident comes to all; and also the heart of the sons of man is full of evil and madness in their life, and after it they go to the dead.
9The heart is deceitful above all things and desperately sick; who can understand it? 10I the LORD search the heart and test the mind, to give to each person according to his ways, according to the fruit of his deeds.
23For all have sinned and fall short of the glory of God.
12Through this, just as through one human sin entered into the world, and through sin death entered, and thus death passed through into all humans, upon which all sinned. 13For until law sin was in the world, but sin is not charged when law is not present. 14But death reigned from Adam until Moses, even over those who had not sinned in the likeness of the transgression of Adam, who is a mark of the one to come.
1And you, who were dead in your trespasses and sins, 2in which you once walked according to the age of this world, according to the ruler of the authority of the air, the spirit now active in the sons of disobedience, 3among whom we also all once lived in the desires of our flesh, doing the wills of the flesh and of the minds, and we were by nature children of wrath, just as the rest,
8If we say that we have no sin, we deceive ourselves and the truth is not in us.

Human nature, left to itself, is fallen. Article VII of the Confession of Faith teaches that humanity is fallen from righteousness and, "apart from the grace of our Lord Jesus Christ," is "destitute of holiness and inclined to evil." Article VII of the Articles of Religion, "Of Original or Birth Sin," teaches the same in Reformation language. Sin is "the corruption of the nature of every man," by which a person "is very far gone from original righteousness, and of his own nature inclined to evil, and that continually." (Where the older articles have "man," the catechism reads "humanity"; the doctrine is the same.)
Scripture traces this condition from the beginning. Before the flood, "the LORD saw that the wickedness of man was great on the earth, and that every intention of the thoughts of his heart was only evil continually" (Genesis 6:5). David confessed that the trouble goes back to birth: "in sin my mother conceived me" (Psalm 51:5). Ecclesiastes calls the heart "full of evil and madness" (Ecclesiastes 9:3), and Jeremiah says that "the heart is deceitful above all things and desperately sick" (Jeremiah 17:9). No one is exempt: "all have sinned and fall short of the glory of God" (Romans 3:23), because "through one human sin entered into the world, and through sin death entered" (Romans 5:12). Paul describes his readers as once "dead in your trespasses and sins" and "by nature children of wrath" (Ephesians 2:1, 3), and John warns that "if we say that we have no sin, we deceive ourselves" (1 John 1:8).
No person is ever actually left in this state. The article describes human nature apart from the grace of our Lord Jesus Christ, and that grace is already at work everywhere. ΒΆ102 of the Book of Doctrines and Discipline teaches that preventing grace mitigates "the effects of original sin, even before we are aware of our need for God." The doctrine of original sin describes what human nature is on its own, so that what grace does can be seen clearly.
Wesley preached original sin as the foundation of Methodist preaching, since a person who does not know the disease will not seek the cure. A member who knows that holiness is absent by nature will look for it where it comes from, in the grace of Christ, which the next questions describe.