For those of a Christian persuasion sin means a violation of a divine rule or commandment. Romans 4:15 says .... where no law is , there is no transgression. The word transgression is defined as a violation of a definitive, published law. It is analogous to the word sin as seen in Romans 5:14.
In the picture of sin which I took away from Orthodox Christianity, God made whatever rules he chose and men obeyed them or became condemned. In the case of the Garden account, any arbitrary divine rule would have had exactly the same effect on
This concept of sin is exceedingly strange on so many levels. A divine being of the generally understood nature and stature of the biblical God seems terribly diminished by the idea that He needs subservience, reverence, and praise to such an extent that he resorts to the most extreme form of coercion in order to get it. The God described so eloquently in I Corinthians 13, is the polar opposite of that needy, threatening spirit.
So did God invent sin for his own selfish purposes? I seriously doubt it. Is sin defined by any old rule God chooses arbitrarily? Again I don't think so. Sin is more logically anything that opposes God's true nature. Under this paradigm, we naturally need to see God's true nature to really understand sin. Can sin serve God's purpose? Yes, but not in meeting his needs but rather in meeting the needs of mankind to evolve fully in its divinely endowed potential.