Carl Sagan's Logic

NOTE: More babbling from my BYU-Idaho class.

Carl Sagan is known, of course, as a scientific populist, someone who advocates, per Wikipedia, a return to the “older Aristotelian movement of horizontal interactions among equals who are different.” In other words – Sagan is someone who wants to speak on scientific principles not only with other scientists, but with lay people who share his interest in the scientific method.

In this clip from the popular television show Cosmos (well, it was popular when I was a kid in the early 1980s) Sagan turns to the subject of astrology. Obviously, as a scientist, he is dismissive of astrology. But isn’t it interesting to consider the persuasive methods he uses to put his point across?

First, who is his audience? What approach will he take – will he use logos, an appeal to logic; pathos, an appeal to emotion; or ethos, an appeal to character or credibility?

Second, what kids of claims does he make in the following statements:

• Astrology suggests a dangerous fatalism. If our lives are controlled by a set of traffic signals in the sky, why try to change anything?

• I was born in a closed room. Light from Mars couldn’t get in. The only influence of Mars which could affect me is its gravity. But the gravitational influence of the obstetrician was much larger than the gravitational influence of Mars. Mars is a lot more massive, but the obstetrician was a lot closer.

• The desire to be connected to the cosmos reflects a profound reality. But we are connected. Not in the trivial ways that the pseudoscience of astrology promises, but in the deepest ways. Our little planet is under the influence of a star. The sun warms us. It drives the weather. It sustains all living things. Four billion years ago, it brought forth life on Earth.

Sagan, interestingly, relies heavily on ethos – or our trust in his character – as he makes his arguments. He mentions the last “scientific astronomer” Johannes Kepler in this bit, but he does not reveal anything to us about how Kepler drew away from astrology and into astronomy. Sagan presents few documented facts for us to consider throughout this clip. He is instead using ethos and pathos to convince us of his point of view.

He does, in the second example, use logos to convince us that believing the planets influence our fate at the time of our birth is absurd, given that the planet’s physical properties have such weak influence on us at the time.

In the third example, he relies heavily on pathos – drawing on our emotions, our desire to feel connected to the world around us but in real ways, not the “pseudoscience” used in astrology.

What kinds of claims does Sagan make in this clip? I believe he uses the three we discuss in class:

He makes evaluative claims, asking us to find the common assumption in the view that celestial traffic lights controlling our fate is a silly thing.

He uses definitive claims when he compares what scientific evidence-gathering has found out about the planets in comparison to the astrologers’ belief that the planets personify war, death, authority – and portent the presence of such in our lives as they rise and fall.

He uses advocative claims when he works to convince us to take the course of action that leads us to believe we are connected to the world and our own sun through real, physically-measurable ways.