Carl Sagan (1934–96) was professor of astronomy and space sciences and director of the Laboratory for Planetary Studies at Cornell University. For many, however, Sagan will forever be associated with astronomy because of the public television series Cosmos, based on a book of the same name. Sagan appeared regularly on the Tonight Show with Johnny Carson, explaining to his host the story of the “billions and billions” of galaxies in space. Toward the end of his life Sagan taught critical thinking at Cornell, which led him to appreciate rational arguments even more.

Science and Religion

Sagan wrote frequently on issues of religion and science. He began one lecture with a quote from Leonardo da Vinci. In his notebooks da Vinci wrote: “Whoever in discussion adduces authority uses not intellect but memory.” Sagan respected the inquiring intellect of his scientific predecessor, but also his courage in the early sixteenth century, when most knowledge was derived from authority and not intellect.

Leonardo da Vinci had his own encounters with religion and science. During a trip to the Apennine mountaintop, he discovered the fossilized remains of shellfish that ordinarily lived on the ocean floor. How could such a thing have happened? The current theological wisdom explained that the Great Flood of Noah had lifted the clams and oysters to such a height. But according to the Bible the flood lasted only forty days. Would this be sufficient time to carry the shellfish to the mountaintops? During what stage in the life cycle of the shellfish had they been deposited? — and so on.

Da Vinci concluded that the biblical interpretation could not work. He proposed another alternative: over great periods of time the mountaintops had pushed up through the oceans. While his hypothesis was inconsistent with the prevailing theological one, it turned out to be the correct answer, as science would establish.

Sagan talked about three kinds of Gods. There is the God of the Judeo Christian-Islamic tradition who is omnipotent, omniscient, compassionate, creator of the universe, is responsive to prayer, performs miracles, and intervenes in history in other ways. A second sort of God — and one worse from a human standpoint — would be a god who was oblivious to humans. Such was Aristotle's god, whose activity was spent thinking about his own thinking. A third kind of God would be the one of Baruch Spinoza and Albert Einstein.

In fact, there is a dizzying array of religious alternatives to feast upon. There are gods that never die and gods that do. There's a smorgasbord of questions about “sacraments, religious mutilations, baptisms, monastic orders, ascetic expectations, the afterlife (yeah or nay), days to eat fish, days not to eat at all, how many afterlives you have coming to you, justice in this world or the next world or not at all, reincarnation, human sacrifice, temple prostitution, jihads, and so forth.” It all seems exceedingly arbitrary — this “grab bag” of religious alternatives. Sagan estimated that in the history of the world there were tens, maybe hundred of thousands, of religions.