A couple months ago Ben Hoffman wrote an article laying out much of his worldview. I responded to him in the comments that it allowed me to see what I had always found “off” about his writing:

To my reading, you seem to prefer in sense making explanations that are interesting all else equal, and to my mind this matches a pattern I and many other have been guilty of where we end up preferring what is interesting to what is parsimonious and thus less likely to be as broadly useful in explaining and predicting the world.

After some back in forth, it turns out what I was really trying to say is that Ben seems to prefer adding epicycles to make models more complete while I prefer to avoid them.

Epicycles come from Ptolemaic astronomy which puts the Earth at the center of the universe with everything, including the Sun, orbiting around it. To make this geocentric model fit with observations of retrograde motion, though, required the introduction of epicycles, imagined spheres in orbit around Earth on which the planets rotated. It’s now part of the mythology of science that over time extra epicycles had to be added to correct additional observational anomalies until it became so complex that epicycles had to be thrown out in favor of the simpler heliocentric model. And although it seems this story is more misunderstanding than truth, “epicycle” has become the metonym for adding parts to a theory to make it work.

Epicycles of the moon

Epicycles have a bad rap. After all, they proved to be part of an incorrect model and are now associated with anti-scientific adherence to maintaining tradition because they were needed to support the cosmology backed by the Catholic church. But I mean to use “epicycle” here in a neutral rather than pejorative way to simply mean making a theory more complete by adding complexity to it. It’s not necessarily bad to “add epicycles” to a model, and in fact doing so has its uses.

Epicycles let you immediately make an existing theory more complete. For example, if you have a unified theory of psyche, adopting something like dual process theory instantly gives you additional explanatory power by allowing the model to decompose concepts that may have been confused in a unified psyche. In turn, 3-part and 4-part psyche models add more epicycles in the form of more parts or sub...