Truthfulness and Contract Law

Suppose Smith tells Jones something in confidence. Jones then reveals the message. Is it ethical for Smith to deny having informed Jones, causing Jones's revelation to lack credibility?

Or suppose Jones tortures Smith to get him to reveal his secret mission. Is it ethical for Smith to lie to Jones?

Or suppose that Smith and Jones are enemies, and Jones is a vile person. When Smith says to Jones, "What I am telling you now is the truth," is Smith obligated to then tell the truth? In both cases, a useful framework for thinking about the situation is the common law of contracts. The common law reflects fairness and efficiency, and has been thought out over many years in addressing lots of difficult situations in a consistent way.

The way to use the insights of contract law is to think of Smith and Jones as making a contract. Smith agrees to tell Jones something, and Jones agrees to do something for Smith in exchange. An implicit part of the agreement is that Smith will tell the truth.

In the case of the violated confidentiality, Jones has breached the contract by revealing the information publicly. Smith is therefore released from his obligation to tell the truth and back Jones up. If one party to a contract breaches seriously enough, the other party need not perform.

In the case of the torture, the contract is made under duress. Smith is therefore not obligated to perform his side by telling the truth.

In the case of the vile Jones, the contract is valid. Contract law does not allow breach just because the other party is a bad person.