Is it worse to break a promise in order to avoid telling a lie, or to tell a lie in order to keep a promise?

There's no all-purpose answer.

Breaking some promises is worse than breaking others. Telling some lies is worse than telling others. But there's no good reason to think that every broken promise is worse than any lie or vice-versa. Telling some lies is worse than breaking some promises; breaking some promises is worse than telling some lies. If you really have to choose, the least bad choice will depend on the details.

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