Measure what can be measured

Measure what can be measured. Incorrectly attributed to Galileo:

Cournot wrote:

La vraie physique a été fondée le jour où Galilée, rejetant des spéculations depuis si longtemps stériles, a conçu l’idée […] de préciser la forme générale à donner aux expériences, en leur assignant pour objet immédiat la mesure de tout ce qui peut être mesurable dans les phénomènes naturels. (Cournot De l’origine et des limites de la correspondance entre l’algèbre et la géométrie. Paris/Algier: Hachette, p. 375)

Translated:

True physics was founded the day when Galileo, rejecting the long sterile speculations, conceived the idea […] of specifying the general form to be given to experiments, assigning them as their immediate object the measure of all that can be be measurable in natural phenomena.

Similar to the more famous dictum by Kelvin:

In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and methods for practicably measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.

References:

• Andreas Kleinert Der messende Luchs: Zwei verbreitete Fehler in der Galilei-Literatur. (https://link.springer.com/content/pdf/10.1007/s00048-009-0335-4.pdf)
• Kelvin, ELECTRICAL UNITS OF MEASUREMENT. A Lecture delivered at the Institution of Civil Engineers on May 3, 1883" (https://archive.org/stream/popularlecturesa01kelvuoft#page/72/mode/2up)