You may not have heard of Stanley Milgram, but chances are you will be aware of his psychology experiment from 1961. In it, he arranged for a dour scientist in a grey lab-coat to instruct certain people ("teachers") to administer increasingly severe electric shocks to an affable stranger in an adjacent room if he gave the wrong answers to questions in a test.
The aim for Milgram - the child of Eastern European Jewish parents - was to find out the extent to which we are prepared to follow the orders of an authority figure. His underlying motive was to discover just how the Nazis' programme of annihilation, based on Germans "following orders", was possible.
In the new movie about Milgram's life and work, Experimenter, Peter Sarsgaard - known for playing evil types in movies from Knight & Day, with Tom Cruise, to porn biopic Lovelace - assumes the role of the controversial psychologist; controversial because, notwithstanding his good intentions, Milgram's experiment created distress, not for the stranger in the room - the "electric shocks" were fake - but for the individuals who believed they were causing his suffering.
"I don't really consider what [Milgram] did - certainly by today's standards - morally reprehensible or anything," says Sarsgaard, arguing that he sees far worse in terms of inflicting pain and humiliation on unsuspecting members of the public, on American TV shows such as Punk'd.
"Shaming is something that we like to do now," he says of our culture of televisual humiliation. "We like to watch someone do something idiotic, then reveal to them that we were watching them and they get to feel shame.
Ignoring subjects such as this has not been great for mankind
"At least," he adds of Milgram's experiment, "this was done for scientific purposes. But what's most troubling to people is, the test subjects came away knowing they were capable of following the orders of a leader who didn't have their moral values, who were at times malevolent. But it's good to know that. Why should people be left in the dark about aspects of themselves that are not wonderful?"
What must be wonderful is acting in a movie that provokes such intense debate. Has he been to a dinner party recently with, say, Tom Cruise and discovered that he's capable of dastardly deeds?
"Tom Cruise is such an interesting choice of person," he chuckles, evading the question. "It's definitely something that interests everyone."
He admits that during filming, he suggested to the director Michael Almereyda that they try a version of Milgram's experiment themselves, but Almereyda and the producer refused.
"They were worried about becoming part of something they were portraying," he explains, "but to me it's important to try and understand the truth about ourselves. When people said [after Milgram's experiment], 'Oh, I got tricked and now I feel like I'm capable of murder?' Well, we all are! Sorry, but that's the big headline news that we all need to learn, otherwise we will end up doing horrible things. Ignoring it has proven not to be very successful in the history of mankind."
Experimenter appears at a time of increased hostility towards Jews, at least in Europe. In the US, Sarsgaard - who is Catholic, although his wife, actress Maggie Gyllenhaal, and two children are Jewish - is more aware of negative feelings towards Israel.
"I think there's increased hostility towards immigrants in general," he considers. "People are going to have to get used to [immigration] because, due to climate change and war, there are going to be entire countries that aren't inhabitable at some point in the future."
Will he teach his young daughters, as per the movie, to follow authority, or to have a healthy distrust of it?
"I always encourage anyone to be suspicious of authority," he says. "Part of being a citizen is questioning the government. It doesn't make any sense not to. Look at the history of the United States: there was slavery in this country. What if we'd not questioned that? Or the woman's right to vote? It's absurd not to question authority; it's your moral responsibility."
Sarsgaard agrees he has cornered the market in "morally ambiguous" characters. His next role is as Robert Kennedy.
"I feel pretty lucky - I get to play characters of all types," he says. He worries, however, that "people get hung up on the fact that I do occasionally play rapists, or I should say, someone who commits rape," he says of the part of Chuck Traynor in Lovelace.
Has he ever turned down a role on the grounds that it was an amoral step too far?
"I was offered to play a paedophile once," he reveals. "But I would have had to act with a child and have predatory feelings about a child and there's going to be a real child actor opposite me. So I wouldn't do it." Finally, does he believe the 65 per cent of "teachers" prepared to administer the most extreme electric shocks are judged, even damned, in the movie?
"No, I don't think so," he says. "And I don't think they are in the [documentary] films that Stanley made.
"The footage we have is of the last two days of the experiment, and if anything you're filled with compassion.
"Because the good news is, there are very few sadists. Not so many people go gleefully to the last switch and hit it a number of times. In fact, many of them weep or pull their hair out. No one goes happily. They just don't want to defy an authority figure."