The Beatles were so much a part of the youth movement that blossomed in the 1960s that it's amusing to think that one of the main issues that energized the movement--peace--came to the Beatles through a 92-year-old man.
As Paul McCartney explains in this clip from a January 14, 2009 interview on The View, it happened when he decided to pay a visit to philosopher Bertrand Russell. A co-founder of analytic philosophy, Russell had been a life-long social and political activist. During World War I, he was not allowed to travel freely in Britain due to his anti-war views. He lost his fellowship at Trinity College, Cambridge, and was eventually jailed for six months for supposedly interfering with British Foreign Policy. After World War II, Russell lobbied strenuously for the abolition of nuclear weapons. In the 1960s, he opposed the Vietnam War.
After the Beatles became big in 1963 and 1964, McCartney began taking advantage of his celebrity status by calling on people he admired. In an interview with Barry Miles for the book Paul McCartney: Many Years From Now, McCartney describes his meeting with Russell:
Somehow I got his number and called him up. I figured him as a good speaker, I'd seen him on television, I'd read various bits and pieces and was very impressed by his dignity and the clarity of this thinking, so when I got a chance I went down and met him. Bertrand Russell lived in Chelsea in one of those little terrace houses, I think it was Flood Street. He had the archetypal American assistant who seemed always to be at everyone's door that you wanted to meet. I sat round waiting, then went in and had a great little talk with him. Nothing earth-shattering. He just clued me in to the fact that Vietnam was a very bad war, it was an imperialist war and American vested interests were really all it was all about. It was a bad war and we should be against it. That was all. It was pretty good from the mouth of the great philosopher. "Slip it to me, Bert."
McCartney reported his experience to the other members of the Beatles, and it was John Lennon who really took the anti-war message and ran with it. For a reminder of those days, watch the video below of Lennon and Yoko Ono at their "Bed-In" for peace in 1969: