 is not necessary that they [the images] should be
| in conformity with the [external] things in any other respect whatever.
| As a matter of fact, we do not know, nor have we any means of knowing,
| whether our conception of things [our models] are in conformity with
| them [external things] in any other than this one fundamental respect.
|
| Heinrich Hertz (1857-1894),
|'The Principles of Mechanics', Dover, NY, 1984, pages 1-2.
| original German edition:  'Prinzipien Mechanik', 1894.

HP, rendering Hertz: