Prescriptive and Descriptive Philosophy of Science

What is the difference between a prescriptive and a descriptive philosophy of science?

Simply put: descriptive philosophy of science attempts to describe what science actually does, and prescriptive philosophy of science describes what science should do. The problem with determining which is which, is that prescriptive philosophy of science often seems to mask itself in language that sounds an awful lot like descriptive philosophy of science. For instance, if you read Karl Popper, and had never heard of science before, you would think that he was describing science, not setting up some rules for it. I believe the latter is true, simply because there are obvious historical instances to counter falsificationism as an actual scientific process. But, leaving aside these marginal cases, it might be better to illustrate the prescriptive side of philosophy of science with a more definitive example. The chapter heading from Pearson’s The Grammar of Science, ‘Essentials of Good Science’ seems in itself to be quite prescriptive (this is what good science should be…) but, even more specifically, the following quote illustrates what I have been getting at:

The first aim of any genuine work of science, however popular, ought to be the presentation of such a classification of facts …(14 Pearson)

This is a perfect example of prescription. Pearson is telling us what science should be like, rather than simply describing it. The problem with this sort of philosophy of science is that it generally bears little resemblance to the actual practice of science. Setting up absolute rules for the practice of science generally won’t work well because science is such a vast enterprise. What may work for sociology may not work for physiology or endocrinology, and so on. Thus, prescriptive philosophy of science gives us a skewed picture of just what science is.

So rather than futilely tell science what it should do, and how it should go about its business, many philosophers of science have decided to describe rather than prescribe. They attempt to give us an account of what science actually looks like. This approach was popularized by Thomas Kuhn, who states his reasons for adopting it in his book The Structure of Scientific Revolutions:

History if viewed as a repository for more than anecdote or chronology could produce a decisive transformation in the image of science by which we are now possessed. That image has previously been drawn, even by scientists themselves, mainly from the study of finished scientific achievements as there are recorded in the classics and, more recently, in … textbooks … Inevitably, however, the aim of such books is persuasive and pedagogic; a concept of science drawn from them is no more likely to fit the enterprise that produced them than an image of a national culture drawn from a tourist brochure or a language text… (1 Kuhn)

Thus, Kuhn is reacting against the prescriptive tradition that draws its conclusions about what science ought to look like from ‘finished’ historical examples. These sorts of examples are misleading, and only show a picture of science that science wants to show. What Kuhn wants to do is analyze and describe how science works when we ‘aren’t looking’ (i.e. the process behind the classics and the textbooks).

So, to summarize: prescriptive philosophy of science tells us what science should look like, but only according to the image that science presents as its final product. But, descriptive philosophy of science attempts to get behind that image, and show us what science is up to when no one is looking. It seems more critically valuable not to simply accept the image that your subject is presenting you with, but rather, to examine that subject in their regular environment. So, I think that descriptive philosophy of science can be much more useful (and interesting) to us than prescriptive philosophy of science.

Thomas Kuhn, The Structure of Scientific Revolutions (Chicago, University of Chicago Press, 1962) Third Edition: 1996.
Karl Pearson, The Grammar of Science, 1892.

Other 'philosophy of science'-esque nodes:

Paul Feyerabend
Imre Lakatos
How Science Undergoes Changes of Theory
The Strong Programme
Thomas Kuhn
Normal Science
Logical Postivism
Philosophy of Science
Philosophy of Science and Certainty
All Swans Are White

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