My work is concerned mainly with an abstract subject: the problem of human knowledge and, in particular, of scientific knowledge.

I am an optimist. I am an optimist in a world where among the intelligentsia it has become a strict rule that one must be a pessimist if one wants to be “in”. But I do believe that our age is not so bad as is generally maintained; I do believe that it is better and more beautiful than its reputation. A quarter of a century ago, I gave a lecture, the title of which sounds today even more provocative than it did then: “The History of our Time: An Optimist's View”.