Whatever exists at all exists in some amount. To know it thoroughly involves knowing its quantity as well as its quality.

From The Nature, Purposes, and General Methods of Measurements of Educational Products by Edward Thorndike, 1918.  Emphasis added.

Whatever exists at all exists in some amount. To know it thoroughly involves knowing its quantity as well as its quality.  Education is concerned with changes in human beings; a change is a difference between two conditions; each of these conditions is known to us only by the products produced by it — things made, words spoken, acts performed, and the like. To measure any of these products means to define its amount in some way so that competent persons will know how large it is, better than they would without measurement. To measure a product well means so to define its amount that competent persons will know how large it is, with some precision, and that this knowledge may be conveniently recorded and used. This is the general Credo of those who, in the last decade, have been busy trying to extend and improve measurements of educational products.

We have faith that whatever people now measure crudely by mere descriptive words, helped out by the comparative and superlative forms, can be measured more precisely and conveniently if ingenuity and labor are set at the task. We have faith also that the objective products produced, rather than the inner condition of the person whence they spring, are the proper point of attack for the measurer, at least in our day and generation. 

This is obviously the same general creed as that of the physicist or chemist or physiologist engaged in quantitative thinking — the same, indeed, as that of modern science in general, the nature of educational measurements is the same as that of all scientific measurements. 

Well, it would be were it not for all those wish for ideological dreams to triumph over empirical reality.