A summary of "Science and the Search for God" by Carl Sagan

Science in Search of God is a posthumously published collection of nine lectures on natural theology delivered by astrophysicist and science popularizer Carl Sagan in 1985 at the University of Glasgow as part of the renowned Gifford Lectures. The book was published in 2006, exactly 10 years after the author’s death, by his widow, Ann Druyan. The original English title, The Varieties of Scientific Experience , is a direct reference to William James’s classic work, The Varieties of Religious Experience: Sagan consciously contrasted scientific experience of the universe with religious experience. In the introduction, Druyan describes how Sagan, raised in a Brooklyn Jewish family and memorizing the Shema prayer from Deuteronomy, spent his life pursuing the question of God with the same intellectual rigor he brought to the laboratory — and with the same reluctance to accept anything on faith without sufficient evidence.

Heaven as the first theological argument

Sagan opens his first lecture with a quote from Plutarch: the truly pious must stand between the "abyss of atheism" and the "swamp of superstition." He defines superstition without qualification — as a belief without evidence. The word "religion" comes from the Latin word for "to bind," and in this sense, Sagan believes, the goals of science and religion coincide: both seek to find deep connections between disparate phenomena. The difference lies in the method.

He then proceeds to show a succession of astronomical images — the Eagle Nebula, the Crab Nebula (a remnant of a supernova that occurred in 1054 and was observed by Chinese astronomers and the Anasazi Indians), the Pleiades cluster, the Orion Nebula, and the galaxy M31. Thomas Wright’s 1750 drawings were the first to show the solar system and nearby stars to scale — and Sagan traces how, from drawing to drawing, humanity has increasingly discovered the insignificance of its own position. Our galaxy contains about 400 billion stars, and beyond it, there are hundreds of thousands of millions of other galaxies. Multiplying these numbers, Sagan arrives at a value of one followed by twenty-three zeros — and notes that no Western religion takes this scale into account, even formally.

The theologian, he says, paints a "god of a small world," not a god of the galaxy. Thomas Paine, back in the 18th century, asked why the Almighty, who rules millions of worlds, should die on our planet because a man and a woman ate an apple — a question Sagan takes up. He doesn’t suggest despairing over our own insignificance: "If a Creator exists, would He really prefer an ignorant blockhead?" Science, he concludes, is, in part, "informed worship."

The Copernican Revolution and its incompleteness

The second lecture is devoted to the history of how science has repeatedly dispelled humanity’s illusion of exceptionalism. Aristotle convincingly demonstrated that the Earth is motionless and the heavens are eternal and unchanging. In 1572, the Danish astronomer Tycho Brahe observed a supernova explosion in the constellation Cassiopeia — a previously nonexistent star shone and slowly faded. In 1577, observing a comet simultaneously from several points across Europe, Brahe used parallax to prove that the comet moved among the planets, not through the Earth’s atmosphere, as Aristotle claimed. Both findings shattered the image of an unchanging heavens.

Copernicus formulated the heliocentric system during his lifetime, but only dared to publish it on his deathbed, and his publisher, Osiander, added a preface, presenting it as a "calculus trick." The Catholic Church, which had adopted Aristotelian geocentrism through Thomas Aquinas, threatened Galileo with torture for his thesis on the Earth’s rotation. Sagan lists the blows to human vanity one after another: it was discovered that the Earth has existed for 4.5 billion years (not several thousand); that the human species emerged only a few million years ago, representing less than one-thousandth of the planet’s history; that the solar system does not occupy a central position in the galaxy — this was only discovered in the 1920s; and that the universe has no center at all.

Darwin struck the next blow: humans are evolutionarily related to all other plants and animals. Special relativity finally abolished privileged frames of reference. Sagan considers the teleological argument — "a watch suggests a watchmaker": if a bacterium is more complex than a pocket watch, doesn’t it indicate a Supreme Design? Darwin, Sagan responds, showed that complex order emerges from a less orderly natural world through natural selection — without a capital-W Watchmaker, given enough time.

Newton, having discovered that all the planets move in a single plane and direction, while comets move chaotically, considered this evidence of divine intervention. However, Immanuel Kant and Pierre-Simon Laplace independently proposed a different explanation: the solar system formed from a rotating disk of gas and dust — the solar nebula. Centrifugal force resists compression in the plane of rotation, but not along the axis, and a disk eventually emerges. Particles within it coalesce into planets, which follow a single direction of motion. Cometary orbits were also initially orderly, but were disrupted by the gravitational influence of the stars. Sagan concludes: Newton erred twice by failing to admit that order could arise naturally. The conclusion about a Creator was erroneous.

The God Hypothesis

Lecture Six begins with the story of Leonardo da Vinci: having discovered fossilized seashells in the Apennines, he tried to calculate whether the biblical flood could have washed them onto the mountain slopes in forty days. He concluded that the mountains had risen from the sea over long geological periods. The alternative hypothesis contradicted theology, but it turned out to be correct.

Sagan systematizes the concept of "God": in the Judeo-Christian-Islamic tradition, it is understood as an omnipotent, omniscient, all-good figure who hears prayers. However, the range of interpretations is vast — from an anthropomorphic elder on a heavenly throne to the God of Spinoza and Einstein, understood as the totality of the physical laws of the universe. If we accept the latter definition, atheism is logically impossible. Theologian Paul Tillich, who himself gave the Gifford Lectures, openly denied the supernatural nature of God. Sagan is concerned with the question: where is the evidence for one version or another? God could have inscribed the Ten Commandments on the moon in large letters — ten kilometers per commandment — for them to be seen through a telescope. God could have launched a hundred-kilometer crucifix into orbit. Nothing of the sort exists, and this, according to Sagan, is a serious theological question. The lecture concludes with a quote from Protagoras from the 5th century BC: "I cannot know about the gods, whether they exist or not, or what they look like. Too many things hinder such knowledge."

Religious experience and primitive consciousness

The seventh lecture takes listeners back hundreds of thousands of years. For most of their existence, humans lived in small hunter-gatherer communities, and it was then that our emotional nature was formed. Sagan addresses the Kung tribe, living in the Kalahari Desert of Botswana: there is virtually no social hierarchy, no chieftain, and private property is limited to what can be carried. The spoils belong not to the hunter who killed the animal, but to the craftsman who made the arrow — and yet, they are divided equally. Mystical experiences, hallucinations, and trance dances are perceived in Kung culture as valuable experiences, not pathologies. The tribe experiences various levels of consciousness, including those achieved through chemical hallucinogens.

When confronted by hunters who have killed their neighboring Herero cows, mistaking them for game, a tribe that has not yet learned to herd livestock encounters a culture that has outgrown it. Sagan sees such episodes as a model for a broader human misunderstanding: different cultures, religions, and eras operate within different frames of reference and struggle to recognize each other’s values as equal.

A single question runs through all nine lectures: are science and genuine spiritual experience compatible? Sagan’s answer is yes, but only if the search continues, not if it is declared complete. His final words, handwritten beneath a quote from Leibniz calling for a halting of questions at the concept of God as sufficient reason, read: "Don’t stop."