And we are not so sure what the parameters are anymore. But what John wants us to know is that sin is a very big deal. It is not something that Christians can take lightly. John defines sin in our text as lawlessness. The two words are interchangeable.
Sin is lawlessness - lawlessness is sin.
And in relating these two words in this way John describes for us the essence of sin. John wants us to know that human sin is more than an errant departure from God's will for life. So John is not just referring to a dirty laundry list of sins as we find in other places in the bible. And at that level, John tells us sin is lawlessness, it is anarchy, it is dissension, it is terrorism. Post-modernists teach that morality is a private issue, it is a personal matter.