International Society for Science & Religion - Library Project

The Logic of Scientific Discovery

by Karl Popper

Introductory Essay by Michael Ruse

This is one of the most important works of philosophy written in the twentieth century. Although it appeared in German in 1934, the real influence of The Logic of Scientific Discovery (LSD) started to be felt when it appeared in English in 1959. Popper was concerned to distinguish genuine science from other forms of thought. Elsewhere (in Conjectures and Refutations) Popper explains that his thinking was sparked by claims in the 1920s that Freudian psychoanalytic theory was genuine science. It seemed to him that this simply was not so – at least not when one compares Freud’s work to Einstein’s. Also influential on Popper was the need to defend the theories of Einstein and others from growing charges (made explicit under National Socialism) that relativity theory and other important scientific advances were degenerate, because they were in some sense “Jewish.” For Popper, science is “objective,” and pays no respect or homage to persons or ideologies. In his felicitous phrase, science is “knowledge without a knower.”

Popper proposed a criterion of demarcation, distinguishing science from non-science, his celebrated notion of falsifiability. Recognizing that no number of positive instances can completely confirm a general statement or law (the very stuff of science) he seized on the fact that even a single counter-instance can refute a general statement. No number of white swans confirms completely “All swans are white,” but one black swan shows it to be untrue. Hence the criterion: “it must be possible for an empirical scientific system to be refuted by experience.” Newton’s theory held sway for many centuries and then was shown to be false (in the special case of relativistic physics). Newtonian physics, therefore, can be judged to have been genuine science. By contrast, no matter what prima facie counter evidence is unearthed, nothing changes the convictions of the Freudian. Hence, Freudian psychology cannot be said to be genuine science.

It is important to note that Popper did not want to argue that all non-science is nonsensical or worthless. Indeed, in LSD he stressed that metaphysics, by its very nature, cannot be falsified. Yet it can play a major role in the advancement of understanding. Popper picked out atomism as an instance of a metaphysical belief that has proven very fruitful. Likewise, although religion has never been a major concern of Popper’s, he would argue that it is not necessarily wrong. It is just that it is not science. Seizing on this insight, American courts have emphasized the falsifiabilty criterion in cases keeping biblical literalism (Creationism in its various forms) out of the states’ biology classes.

There have been many critics of LSD, chiefly on the grounds that scientific theories comprise a body of empirical claims and that showing an overall theory to be false does not necessarily clarify the actual point of untruth. Followers of Thomas Kuhn’s The Structure of Scientific Revolutions emphasize this point and argue that scientists are much less willing to defer to new evidence than Popper supposes. Yet all agree that LSD ultimately must be judged one of the all-time great and humane defenses of the possibility of truth and objectivity.