Hermann Ebbinghaus, answered from the texts and cited to the page.
Psychology has a long past but only a short history: for millennia men speculated about the soul, and only in our own age has the study of mind become a science — and it became one by learning to measure.1 What is not measured is not yet known with the certainty of science; opinion multiplies where number is absent. My work on memory was, at bottom, a demonstration of a method: that the mind, even in its higher functions, can be brought under exact, quantitative, repeatable experiment and made to yield law.
And the method reaches further than memory. I devised a test — the completing of mutilated sentences — by which the mental capacity of schoolchildren could be measured and compared, for capacity too, rightly approached, submits to measurement. I do not say that number exhausts the mind, or that the meaning and quality of experience are nothing; I say that where we can measure, we should, for measurement is what has turned a long tradition of speculation into a young and growing science.2
INTRODUCTION A SKETCH OF THE HISTORY OF PSYCHOLOGY Psychology has a long past, yet its real history is short. For thousands of years it has existed and has been growing older; but in the earlier part of this period it cannot boast of any continuous progress toward a riper and richer development.Psychology An Elementary Text-book
To facilitate this acquaintance is the purpose of this translation. The translators wish to acknowledge their indebtedness to Professors Edward L. Thorndike, Robert S. Woodworth, and E. W. Bagster-Collins of Columbia University, to Professor Walter Dill Scott of Northwestern University and to Mrs. H. A. Ruger for assistance in revising manuscript and proof.Memory A Contribution to Experimental Psychology
Ebbinghaus's programmatic commitment to exact measurement as the method of scientific psychology was largely victorious and defines the experimental tradition; his completion test was a real early contribution to mental measurement and to the stream that produced intelligence testing (Binet drew on such completion tasks). The standing critique is the perennial one against a purely measuring psychology: that the quantitative method, powerful as it is, can miss the meaningful, qualitative, and interpretive dimensions of mind — the objection pressed by Bartlett, the Gestaltists, and the hermeneutic and phenomenological traditions, and echoed in every later argument that not all of mind is number. Ebbinghaus's own position is the modest one — measure where you can, without claiming number exhausts the mind — which remains defensible, so the contest is over scope, not over the value of measurement.