---
title: "Against Method"
chunk: 3/5
source: "https://en.wikipedia.org/wiki/Against_Method"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:36:20.726635+00:00"
instance: "kb-cron"
---

=== Galileo case study ===
The primary case study in Against Method is Galileo's hypothesis that the earth rotates on its axis. According to Feyerabend's reconstruction, Galileo did not justify this hypothesis by reference to known facts, nor did he offer an unfalsified conjecture that had more empirical content than its predecessor. Rather, Galileo's hypothesis would rationally have been considered to be false by the existing evidence at the time, and it is lower in empirical content than Aristotelian theory of motion. Moreover, Galileo did not provide arguments to justify his contention but instead used propaganda.
According to the existing evidence in the early 17th century, the position that the earth rotates on its axis would have rightly been regarded as false. For example, Galileo's theory of the tides suggested by the motion of the earth was inaccurate and the differences "were big enough to be known even to the most bleary-eyed sailor." In addition, the motion of the earth on its axis leads to the wrong predictions of the relative brightness of Mars and Venus when measured with the naked eye. To correct for these mistakes, Galileo introduces new evidence through his telescope. However, the telescope was not theoretically understood at the time. The best theory of optics was Kepler's, which Galileo did not understand personally, which says nothing about how light reflects off convex lenses. Moreover, there were well-confirmed reasons to think – as the Aristotelians thought – that light behaves differently outside of the sublunar sphere and so telescopic vision would not have any justification for being veridical. In addition, when Galileo tested the telescope with many observational astronomers in Padua, it produced indeterminate and double images, optical illusions about the placement and magnification of celestial bodies, and after images even when tested on terrestrial objects. Because of this, Galileo had no new evidence to support his conjecture that the earth completes a diurnal rotation on its axis and the existing evidence suggested that it was false.
Galileo's hypothesis also does not follow Popper's falsificationism, which suggests that we do not use ad hoc hypotheses. Aristotle's theory of motion was a part of a broader theory of change, which included growth, decay and qualitative changes (such as changes in color). Galileo's theory of motion focuses solely on locomotion and, therefore, has less empirical content than Aristotle's theory. This also makes it more ad hoc, because it makes no new predictions and offers only a promissory note that locomotion will eventually explain everything Aristotle's theory was able to explain.
Feyerabend does not just argue that Galileo and his followers acted "irrationally" from the perspective of inductivism and falsificationism, but that it was reasonable that they did so. This is because Galileo's conjecture was able to reveal the natural interpretations that followed from the Aristotelian worldview. Natural interpretations, defined by Feyerabend, are interpretations of phenomena which happen naturally and automatically in our perception and the ways we attach language to what we observe. After accepting a theory for a long period of time, natural interpretations become implicit and forgotten and, therefore, difficult to test. By contrasting natural interpretations with other interpretations, they are made explicit and can be tested. Therefore, to fully scrutinize the Aristotelian worldview, Feyerabend suggests that Galileo was right to conjecture a new theory that revealed its natural interpretations.
The main example of the influence of natural interpretations that Feyerabend provided was the tower argument presented as an objection to the theory of a moving earth. Aristotelians accepted the proposition that a stone, or any solid body made of earth, dropped from a tower lands directly beneath it, shows that the earth is stationary. They thought that, if the earth moved while the stone was falling, the stone would have been "left behind." Objects would fall in a parabola instead of vertically. Since this does not happen, Aristotelians thought the earth did not move. Galileo's hypothesis reveals that this assumes that all motion is "operative" (i.e., noticeable in perception). Galileo denies this assumption and argues that the stone falls in a parabola relative to absolute space, although the notion of absolute space was not made explicit and coherent until Newton.
However, Galileo did not present his work in this vein. If he had, Feyerabend conjectures that his new theory would have received little attention and would not have stimulated further inquiry into the Copernican system. Because of this, Galileo uses propaganda to make it seem as if his theories are implicit in the Aristotelian worldview. Specifically, Galileo makes it seem as if his conception of relative motion is embedded in Aristotelian common sense when it isn't (Aristotelian relative motion involves many moving bodies with dynamic effects noticeable in perception). According to Feyerabend, Galileo uses the technique of anamnēsis where he invites readers to "remember" that they already believed in relation motion in Galileo's sense. Using this method, he disguises how radical a break his new theory is from then common sense.