Daniel Dennett (1942-2024)


For a long time there's been a kind of Cold War with a slow moving front between philosophers and scientists, especially physicists. The scientists accuse the philosophers of being as useful to the theory and practice of science as "ornithologists are to birds", as a popular saying goes. The philosophers in turn emphasize to the scientists that their disciplines, especially in the 20th and 21st centuries, are so complex and abstract that they cannot be understood without the input of philosophy.

It is in the light of this debate, especially, that the death of Daniel Dennett hit so hard. Unlike most philosophers, Dennett was someone who tried to seriously grapple with the actual facts of science - in his case, evolutionary biology and neuroscience - as opposed to the fevered armchair speculation of philosophy. These facts were on full display in the many phenomenal books he wrote, of which my favorites are "Darwin's Dangerous Idea", "Breaking the Spell" and "From Bacteria to Bach and Back".

Dennett's writing was wonderful and brilliant - extremely witty, confident, bold, even stridently so. He was one of only a handful of writers who regularly elicited moments of "Aha!" in my mind. More than almost anyone else from his generation he was unafraid of taking on bold ideas, particularly ones which would make readers uncomfortable. Whether he was arguing that consciousness is a kind of useful delusion in "Consciousness Explained" or exhorting readers to take the scientific study of religion seriously, as in "Breaking the Spell", Dennett was always provocative. I do not remember a single time when I did not come away from a piece of Dennett's writing without ideas and questions swirling around in my head.

This was true irrespective of whether I agreed with him or not, and there was certainly enough in his work for spirited disagreement. But this is something that needs to be pointed out especially today when so many of us are being asked, explicitly or implicitly, to pick sides, to eschew shades of gray, to personify the "with us or against us" ethos. Dennett took his opponents' arguments seriously, before politely demolishing them. Even when he mocked shoddy thinking - and there was no dearth of that kind of incisive analysis in his writings - he did so after careful consideration of their positions. That quality is on full display in "Breaking the Spell" in which he takes on religious proponents with zeal and certainly, but also with careful analysis.

It was Dennett's critical take on religion that led him to be pegged as one of the four "horsemen" of the New Atheism movement, along with Richard Dawkins, Christopher Hitchens and Sam Harris. Part of what made him a member of that group was his sheer delight at the wonders of natural (as opposed to supernatural) evolution by natural selection. In fact, one of the most delightful and brilliant things he wrote showcasing the centrality of a mindless but highly creative process giving the illusion of intelligence was the following from "From Bacteria to Bach and Back":


I find that last sentence to be cleverness exemplified. But given his vast oeuvre of writings, I never thought membership in the brotherhood of the horsemen to be a particularly significant part of Dennett's intellectual identity, and from what I hear, neither did he. Instead it was just one among many facets of a life devoted to reason, understanding and debate. His books were packed with so many things apart from atheism that it would be a disservice to primarily identify him with that movement.

When I heard about Dennett's death I was about to spend some quality reading time in a coffee shop. I picked up "Breaking the Spell" and spent the next two hours engaging with that classic Dennettsian blend of provocativeness, wit and wisdom. At the end, just like when I had read his works before, I felt invigorated, as if I had just had a first-class workout in a mental gym. And as before I felt like a slight shift had taken place in my consciousness, my understanding of the world and myself. The core of Dan Dennett's identity was devoted to teaching us to question our deepest, most cherished beliefs and to encourage critical thinking, no matter where it led us. In the process he made us think and feel provoked, delighted and yes, uncomfortable. Because through discomfort, whether physical or mental, comes enlightenment.

Simple, atypical but neat estimation of energy released in fission

Simple but neat atypical calculation of energy released in fission (from Glasstone and Sesonske, “Nuclear Reactor Engineering”). It’s a nice illustration of guesstimating based on empirical data.

"The amount of energy released when a nucleus undergoes fission can be calculated by determining the net decrease in mass, from the known isotopic masses, and utilizing the Einstein mass-energy relationship. A simple, but instructive although less accurate, alternative procedure is the following. Disregarding the neutrons involved, since they have a negligible effect on the present calculation, the fission reaction may be represented (approximately) by

Uranium-235 -› Fission product A + Fission product B + Energy.

In uranium-235, the mean binding energy per nucleon is about 7.6 Mev, so that it is possible to write
92 p + 143 n -> Uranium-235 + (235 X 7.6) Mev

where p and n represent protons and neutrons, respectively.

The mass numbers of the two fission product nuclei are mostly in the range of roughly 95 to 140, where the binding energy per nucleon is, as in tin-120, for example, about 8.5 Mev; hence,
92 p + 143 n -› Fission products A and B + (235 X 8.5) Mev

Upon subtracting the two binding energy expressions, the result is

Uranium-235 -> Fission products + 210 Mev."