With four parameters I can fit an elephant. And with five I can make him wiggle his trunk.

From Freeman Dyson - Fermi's rejection of our work.  

Fermi:  When one does a theoretical calculation, you know, there are two ways of doing it.  Either you should have a clear physical model in mind or you should have a rigorous mathematical basis.  You have neither.

Dyson:  So that was it.  In about two sentences he disposed of the whole subject.  So I asked him what he thought of the numerical agreement?

Fermi:  How many parameters did you use for the fit?  How many free parameters are there in your method?

Dyson:  So I counted up. Turns out there are four. 

Fermi:  Johnny von Neumann used to say "With four parameters I can fit an elephant.  And with five I can make him wiggle his trunk."

Double click to enlarge.

Hate to think what Fermi's comments would be about the AGW climate change models and Covid-19 transmission models.  Probably fifteen parameters and a flea doing a pirouette on the elephant's wiggling trunk.