Full Idea
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.
Gist of Idea
You have only begun to do real science when you can express it in numbers
Source
Lord Kelvin (Wm Thomson) (works [1881]), quoted by Reiss,J/Spreger,J - Scientific Objectivity 4.1
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.16
A Reaction
[Popular Lectures 1 p.73] Clearly the writer is a physicist! Astronomers discover objects, geologists discover structures, biologists reveal mechanisms.