Good explanations are hard to vary

Week 1: reason · epistemology

Good explanations are hard to vary

Apply Deutsch's hard-to-vary criterion to tell good explanations from bad ones.

In this lesson

  1. Read the core idea (2 min).
  2. Walk through one worked example.
  3. Take the 4-question quiz; pass with 4/4 or better.

Hook

If evidence cannot generate explanations, and many explanations fit any given dataset, what separates a good explanation from a bad one? David Deutsch's answer is one of the most useful ideas in modern epistemology, and once you hear it you start using it everywhere.

A good explanation is hard to vary while still accounting for what it claims to explain. That single criterion does most of the work that 'falsifiability', 'parsimony', and 'consilience' were supposed to do — and it does it better.