Innumerable philosophers across the ages have dedicated their lives to finding the truth; none of them have identified political advertising as a source.

Yet 15 states hold, by law, that such advertising should be a bastion of truth. Their statutes make it illegal for any political advertising to deliberately state falsehoods about candidates.

That's a commendable ideal, of course. It's reprehensible that some candidates or issue advocates deliberately twist their opponents' records or the issues in search of votes.

But due to the complexity of the English language alone, it's extraordinarily difficult in many cases to say that a particular statement is a lie. That's why prosecutors find it so difficult to prove perjury, even if someone's sworn statement is demonstrably incorrect.

Add that inherent complexity to the nuances of public policy, and the line between honesty and lying becomes even fuzzier.

In a case heard last week by the Supreme Court of the United States, for example, a congressional candidate in Ohio contended that an anti-abortion group had misstated his record in advertising. The group contended he had supported abortion by voting for the Affordable Care Act; he contended that the act itself and other federal law precludes use of federal money to pay for abortions.

But the group contends that money is fungible; funds from the ACA for other purposes could enable providers to shift other funding to abortion practices.

That illustrates the difference between literal truth and practical truth in the application of public policy.

Such interpretations are the legitimate stuff of public debate. It's safer to tolerate some element of lying in political advertising than to use anti-lying statutes to stifle political debate.