Sin is not just a commission of an act; it may also be the omission of an act. Dr. Karl Menninger writes in his book Whatever Became of Sin?:

If a dozen people are in a lifeboat and one of them discovers a leak near where he is sitting, is there any doubt as to his responsibility? Not for having made the hole, or for finding it, but for attempting to repair it! To ignore it or to keep silent about it is almost equivalent to having made it!

Thus even in group situations and group actions, there is a degree of personal responsibility, either for doing or for not doing— or for declaring a position about it. The word "sin" involves these considerations, and upon this I base the usefulness of a revival of the concept, if not the word, sin.