"Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law." (1 John 3:4)
The Bible warns that "the wages of sin is death" (Romans 6:23), and "the soul that sinneth, it shall die" (Ezekiel 18:20). These are strange days, however, and there are many "that call evil good, and good evil" (Isaiah 5:20). Who is to say what is right and wrong, when even our U.S. Supreme Court implies that there are no absolutes?
God is the one who defines sin because it is He who will judge sin. The definition is multifaceted, for sin takes many forms. Most basically, as our text says, sin is the transgression of the law--not just certain laws, but all of God's law. "For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all" (James 2:10).
But there must be more than just formal obedience to God's commands, for "all unrighteousness is sin" (1 John 5:17). Furthermore, there are sins of omission, as well as sins of commission. "To him that knoweth to do good, and doeth it not, to him it is sin" (James 4:17).
When there is no specific law or command to guide our actions in a particular situation, the principle to follow is that of faith--that is, the confident inward assurance that we are doing that which honors the Lord, for "whatsoever is not of faith is sin" (Romans 14:23).
There is much more that could be noted, but it is clear that no one could ever measure up even to these demands, "for all have sinned, and come short of the glory of God" (Romans 3:23). All of us deserve the wages of sin, "but God commendeth his love toward us, in that, while we were yet sinners, Christ died for us" (Romans 5:8). Now "the righteousness of God without the law is manifested. . . . Even the righteousness of God which is by faith of Jesus Christ" (Romans 3:21-22). HMM