when to talk

I wish, I were big enough, like Einstein, to do what he did on one occasion. A hundred-dollar-a-plate dinner was organised for him to speak, and leaders of America in all fields, particularly in the field of science, were invited to hear the great man. When his turn came, he rose and said:'I've nothing to say,' and sat down. You can imagine the consternation, quite apart from the wasted cost of the dinner! Realising the frightful effect his remarks had on the audience, Einstein got up again and said: 'When I've something to say, I'll let you know.'
J.R.D.Tata (Address to the Lions Club of Jamshedpur, August 22, 1963.)