Before coming to the United States, Abdu'l-Baha spent some time visiting Europe. While he was in London, he followed his usaual practice of inviting questions at the conclusion of each talk. After a talk about peace, someone in the audience asked Abdu'l-Baha if he expected peace on earth to come all at once or gradually.
Abdu'l-Baha told that curious listener that peace on earth would probably come about gradually. Abdu'l-Baha then explained why he had made that prediction. He said "A plant that grows too quickly lasts but a short time." (quote taken from the book Abdu'l-Baha in London, page 106)
Apparently Abdu'l-Baha felt that the achievement of peace on earth would usher in a lasting peace.