The question of extraterrestrial civilizations seems to me entirely open. Personally, I think itfar more difficult to understand a universe in which we are the only technological civilization, or one of a very few, than to conceive of a cosmos brimming over with intelligent life. Many aspects of the problem are, fortunately, amenable to experimental verification. We can search for planets of other stars, seek simple forms of life on such nearby planets as Mars, and perform more extensive laboratory studies on the chemistry of the origin of life. We can investigate more deeply the evolution of organisms and societies. The problem cries out for a long-term, open-minded, systematic search, with nature as the only arbiter of what is or is not likely.