And here is now the point that to my mind is even more important than preventing the catastrophe. This is something that is of general interest to all people on Earth. It is a subject where international co-operation is needed and is possible. And I would like to end by saying I believe in two things, in a very practical way: I believe in knowledge and in more knowledge, and I believe in the unifying power of knowledge, as long as we continue to be interested in knowledge and as long as we are willing to take a reasonable and broad view of knowledge. Recent fears of technology, perhaps due to lack of understanding of much of modern science, perhaps due to people's addiction to dangerous fantasies, all this can be overcome and in fact if it can be overcome, the United States has a better tradition than I believe any other country in the world, a better tradition for being interested in what is new and being interested in real co-operation and peace. I believe that a positive future will not be accomplished by fears and by saying no. I think the right thing to do is the old American tradition which was very evident when I arrived in 1935 in the United States; what is new can be good, what is new can be made into something that is new - if we are willing to take a hopeful, strong, positive approach.