Either way, it's a question of . . . Or when a doctor tells a dying patient his cancer has a small chance of going into remission. The answer depends on whom you ask. Parents are pressed to teach their children to always tell the truth, yet many usher their kids to Santa Claus and make promises of gold from the tooth fairy. Teachers demand that students not cheat on tests, yet many exaggerate a student's abilities to boost his ego.
Friends promise to keep secrets, yet they blab the news to the first person who'll listen.
Clergy, the experts on queries about sin, advise their flocks to be truthful. You have to distinguish whether something is a sin or not. At times, lying is necessary but is not evil. Other times, it's not necessary and therefore is evil. He labels the latter, however, a sin.