Physics, Earth & Space Icon Physics, Earth & Space

More on Avi Loeb’s Approach to Design Inferences

Paul Nelson
alien life
Image: ʻOumuamua, by ESO/M. Kornmesser. Derivative: nagualdesign [CC BY-SA 4.0 ], via Wikimedia Commons.

Avi Loeb, Harvard astronomer and outspoken advocate for searching for evidence of extraterrestrial intelligence, has a new trade book out making his case: Extraterrestrial: The First Sign of Intelligent Life Beyond Earth.

In support of the book, Loeb has been conducting a press campaign, including appearing on podcasts such as Sean Carroll’s Mindscape.

What interests me about Loeb’s work is not the specifics of his case for the artificial origin of the ‘Oumuamua object. (See “Avi Loeb: ‘Nature Does Not Produce Such Things.’”) I don’t know enough observational astronomy and physics to have a decent opinion about that.

ID in Mainstream Science

Rather, I am VERY interested in the logical structure of Loeb’s argument, as it currently represents the most salient example of risky intelligent design reasoning in mainstream science. “Risky” is the appropriate adjective here, because while design inferences are commonplace throughout science, where any human activity is concerned (e.g., remote sensing of industrial pollutants, archaeological discovery, cryptanalysis), they are exceedingly rare or non-existent when the intelligence in question is not human. (I am excluding animals, such as crows, chimps, or octopuses.) Loeb’s inference is risky because he is pushing against conventional wisdom, extending intelligent causation as a hypothesis to non-human, extraterrestrial agents.

In one sense, however, Loeb’s position isn’t risky at all. If you listen to the Mindscape segment, the foundations of his argument rest on his convictions that (a) the Principle of Mediocrity, or what he calls the Modesty Principle, is true, namely, that nothing distinguishes Earth and Homo sapiens — we are the expected statistical outcome of cosmic evolution, (b) life arises naturally at a high probability, and therefore (c) science should predict an abundance of technologically advanced civilizations within the galaxy, that would be likely to leave evidence of their existence on scales we can now detect. Loeb’s ID argument, paradoxically, rests on his confident philosophical naturalism. Go figure.

Ironies Galore

In finer detail, ironies galore abound. For instance, at about 29:00 in the podcast, Loeb says that CFCs (chlorofluorocarbons, e.g., Freon) would make an excellent “technosignature” for astronomical detection, as their chemical structures “cannot be produced by nature,” meaning undirected physical processes. Logically this is William Dembski’s explanatory filter (EF). Carroll, a self-identified philosophical naturalist (although he prefers the term “poetic naturalist”), does not object. Carroll doesn’t say, “Hey, wait a minute — that’s Intelligence-of-the-Gaps. There might be an undiscovered natural cause for CFCs, and we cannot infer design until we have eliminated all the natural possibilities first.”

Carroll doesn’t say that, because it would be insane. No one EVER eliminates all the natural possibilities for any phenomenon. That is a logical impossibility: a species of the genus The Problem of Induction. Rather, at about 33:00 — and this is one reason why I like Carroll so much as an interviewer, his openness to persuasion — Carroll says, “I’m completely on board” with the outlines of Loeb’s design inference. CFCs, if we saw them in a planetary atmosphere, would at least be a strong clue to the presence of intelligence.

There He Goes Again

At about 53:00, Loeb does it again: he uses EF logic to arrive at design as the best hypothesis. The example? Finding a plastic bottle on the beach. Again, Carroll does not challenge him, because — let’s be honest, folks — the EF is rationality itself. The EF only scares people when the causal agent implicated looks a lot like God. Then we must keep searching for natural processes, whether we have any reason to do so or not.

Loeb uses his tenured Harvard professorship in the right way. He is blunt and courageous, like many Israelis I know. Listen to the podcast, and you’ll see what I mean. He calls out the “herd tendency” in science, says that Alan Guth told him that cosmic inflation was not falsifiable, but who cares, it’s just a framework to fit data, says that funding mostly goes to reinforce existing trends…blunt talk.

The best news from the podcast: Loeb and a former postdoc have an 800 page textbook on all this coming out in June 2021. A design detection textbook. Now that is COOL.