As pro-life groups step up their efforts to prevent abortions, philosopher Chris Tollefsen asked members of the movement not to overlook a fundamental Christian principle during a Wednesday lecture — it is never acceptable to lie, even to support an important cause.

Tollefsen argued that lying to advance the anti-abortion movement is not morally justifiable before an audience of around 30 students in William L. Harkness Hall. A philosophy professor from the University of South Carolina and a strong pro-life advocate himself, Tollefsen came to campus as part of the William F. Buckley Jr., Program, which sponsors events with a conservative intellectual lean.

Tollefsen said that at its heart, pro-life activists are attempting to effect comprehensive social change.

“The pro-life movement is not a purely political movement,” Tollefsen said. “It seeks a change in belief and culture.”

Even if activists successfully bring about change using guerilla tactics, Tollefsen said, their work is not meaningful if it is the result of lies.

He then introduced a recent controversy in the pro-life movement that was based on a deception: Undercover actors from Live Action — a youth activist group that seeks to end legal abortions — posed as a pimp and a prostitute in February and asked Planned Parenthood employees how to secure services for underage immigrant sex workers they claimed to manage. The two actors filmed the interaction in an effort to defund and defame Planned Parenthood.

Tollefsen argued that despite the sound goal Live Action had in mind, their attempt was wrong on many levels.

Christian philosopher and theologian St. Augustine argued that lying is never justified, Tollefsen said — and by lying in order to expose Planned Parenthood, the Live Action members disrespected Christian tradition.

“It is not the purpose of the lie that identifies whether the lie is OK or not,” he said.

Tollefsen anticipated and answered an opposing argument: A dissenter might ask if it was morally acceptable for those who hid Jews during World War II to lie about their activities to Nazi police, he said.

There are ways of going around the truth, Tollefsen said, and people can refuse to share the truth with those who are not “entitled” to it.

“I am not going to answer your question, because what you are doing is wicked and I want to take no part in it,” he said, offering an alternative script for people who hid Jewish families in their homes.

Tollefsen said anti-abortion advocates have criticized him for his opinions, saying he overintellectualizes a political problem.

“Where would the pro-life movement be without intellectuals?” he asked, pointing to St. Augustine, Thomas Aquinas and other thinkers whose arguments have heavily influenced the abortion debate.

Eduardo Andino ’13 said he found Tollefsen’s argument compelling, and would rather persuade his own opponents by telling the truth. Andino is a founder of Undergraduates for a Better Yale College, a student group that seeks to reform Yale’s sexual culture.

John Aroutiounian ’15 said Tollefson did an exceptionally good job explaining the absolute immorality of lying.

“This is a point of view I have never before heard articulated as cogently,” he said.

Yet Aroutiounian wasn’t fully convinced. He said he still believes that saving lives should be first priority, even if it entails lying.

Tollefsen’s lecture was organized in cooperation with Choose Life At Yale, the only pro-life organization on campus.