Hamartiology deals with the origin of sin as well as its effects and consequences.
I think we are all familiar with the story of Adam and Eve and the biggest “fail” in history. Through the disobedience of one man sin entered the word and destroyed everything.
Our prayers have stains in them, our faith is mixed with unbelief, our repentance is not so tender as it should be, our communion is distant and interrupted. We cannot pray without sinning, and there is filth even in our tears. - C.H. Spurgeon
The effects of sin are too numerous to count but here are a few:
A part of the curse was that all of humanity would be affected by the one act of disobedience from Adam (Romans 5). We are “in Adam” and therefore are guilty of sin from birth. It’s almost as if it became a part of our DNA.
Then the LORD saw that the wickedness of man was great in the earth, and that every intent of the thoughts of his heart was only evil continually. Genesis 6:5
With Paul we lament that the things we know we should do we don’t do and the things we don’t want to do, those are the very things we do (Ro. 7:15).
The natural person does not accept the things of the Spirit of God, for they are folly to him, and he is not able to understand them because they are spiritually discerned.
1. Corinthians 2:14
Man is by nature blind within. The cross of Christ, so laden with glories, and glittering with attractions, never attracts him, because he is blind and cannot see its beauties. - C.H. Spurgeon
As my husband would say, we are “jacked up” humans. But who cares? Why is this important to study? Without a proper understanding of sin we will never fully understand the depth of Christ’s sacrifice or the incredible love of God.
The more familiar we are with all the different facets of the doctrine of Sin, the more we will see and hate our sin, marvel at God’s love, be thankful for Jesus and all his work for us and treasure His word.
Be always greatly humbled by your remaining sin, and never think that you lie low enough for it, but yet don't be at all discouraged or disheartened by it. Although we are exceedingly sinful, we have an advocate with the Father, Jesus Christ the righteous, the preciousness of whose blood, the merit of whose righteousness, and the greatness of whose love and faithfulness infinitely overtop the highest mountains of our sins. - Jonathan Edwards