As stumbling is falling down while one is trying to walk, so is disobeying one point of the law is being guilty of breaking the whole law. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Though James was writing to many Jewish believers, in this case he wrote as if he was writing to each person individually. AT: "each one of you" (See: [[rc://en/ta/man/translate/figs-you]])