Kuhn and Aristotle

[Ari Epstein <awe@pimms.mit.edu>]

An example of the discussion I cited earlier that reminded me of
some of Kuhn's obituaries:

Kyle Forinash wrote:

> However, one should be careful about thinking that the ancient concept of
> impetus is equivalent to our definition of momentum; it is not. The earlier
> concepts of Impetus seem to encompass both kinetic energy and momentum in
> some odd way.
>
> ...
>
> Also Aristotle gave a definition of impetus as a force which pushed
> something forward. In his reasoning as to why an arrow moves (since he
> insisted that natural motion of objects cause them to come to a halt) was
> that air rushes in behind the arrow as it travels, pushing it forward.


I believe that this is *precisely* the definition that inspired Kuhn:
In reading Aristotle, Kuhn saw that Aristotle's use of the word
"impetus" (or its Greek equivalent) indicated that Aristotle was
operating within an entirely different "paradigm," in which moving
objects tend to stop unless something keeps pushing them. Otherwise
Aristotle's physics makes no sense. (Whereas now we might say that it
makes sense but is wrong.)

Ari Epstein