What is Sin?

I was reading the puritan Thomas Watson in his body of divinity, (great book btw) and he listed ten sins that Adam and Eve committed in disobeying God. The command from God was, "You may surely eat of every tree of the garden, but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die." Gen. 2:16-17 I will not quote Watson word by word but this is his work.

1) Unbelief. Adam and Eve believed not that they should die; they could not be persuaded that such fruit had death at the door. Therefore, by unbelief they made God a liar, but worse they believed the devil rather than God.
2)Unthankfulness. Adam's sin was committed in the midst of Paradise. God gave Adam everything, yet he still disobeyed.
3)Discontent. One would think Adam had enough, yet he was not content, he wanted more.
4)Pride. He wanted to be like God, he supposed the tree of knowledge would have anointed his eyes, and made him omniscient, but by climbing too high, he got a fall.
5)Disobedience. God gave Adam his word, therefore it was but right Adam should give God his allegiance.
6)Curiosity. He flirted with that which was out of his sphere, and did not belong to him.
7)Wantonness: Adam had a choice of all other trees that God gave him, yet he must have this tree.
8)Sacrilege. The tree of knowledge was none of Adam's, yet he took of it, and robbed God of his due.
9)Murder. Adam was a public person, and all his posterity were involved and wrapped up in him; and he, by sinning, at once destroyed all his posterity, if free grace did not interpose.
10) Presumption. Adam presumed of God's mercy, he blessed himself, saying he should have peace; he thought, though he did transgress, he should not die; that God would sooner reverse his decree than punish him.
How many sins were in Adam's sin! What an awful thing sin is!

As Scripture teaches Adam was our representative, so we would have committed the same sins he did, and we have committed the very same sins. Oh, how far we have fallen from our original state of righteousness!
Yet rejoice believer, though your sins are like scarlet they shall be as white as snow; though they are red like crimson, they shall become like wool! Christ has suffered once for sins, the just for the unjust to bring us to God!
Let this make us beware of sin and all its horrible effects, and let us also magnify our Savior who washes all our stains of sin away!