---
title: "The Structure of Scientific Revolutions"
chunk: 2/9
source: "https://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:37:26.249284+00:00"
instance: "kb-cron"
---

"The operations and measurements that a scientist undertakes in the laboratory are not "the given" of experience but rather "the collected with difficulty". They are not what the scientist sees—at least not before his research is well advanced and his attention focused. Rather, they are concrete indices to the content of more elementary perceptions, and as such they are selected for the close scrutiny of normal research only because they promise opportunity for the fruitful elaboration of an accepted paradigm. Far more clearly than the immediate experience from which they in part derive, operations and measurements are paradigm-determined. Science does not deal in all possible laboratory manipulations. Instead, it selects those relevant to the juxtaposition of a paradigm with the immediate experience that that paradigm has partially determined. As a result, scientists with different paradigms engage in different concrete laboratory manipulations."

=== Historical examples of chemistry ===

Kuhn explains his ideas using examples taken from the history of science. For instance, eighteenth-century scientists believed that homogenous solutions were chemical compounds.  Therefore, a combination of water and alcohol was generally classified as a compound. Nowadays it is considered to be a solution, but there was no reason then to suspect that it was not a compound. Water and alcohol would not separate spontaneously, nor will they separate completely upon distillation (they form an azeotrope). Water and alcohol can be combined in any proportion.
Under this paradigm, scientists believed that chemical reactions (such as the combination of water and alcohol) did not necessarily occur in fixed proportion. This belief was ultimately overturned by Dalton's atomic theory, which asserted that atoms can only combine in simple, whole-number ratios. Under this new paradigm, any reaction which did not occur in fixed proportion could not be a chemical process. This type of world-view transition among the scientific community exemplifies Kuhn's paradigm shift.

=== Examples from applied microbiology ===
In 1860 Louis Pasteur published experimental results proving that fermentation was caused by microorganisms, instead of some self-starting chemical reaction, which was the reigning theory. As summarized by science writer Charles Mann, "Pasteur’s work led to a pitched intellectual battle—and the eventual triumph of germ theory, which overturned earlier ideas about infectious disease." Mann continues:
Pasteur’s work on the role of microorganisms in infectious disease inaugurated the modern discipline of microbiology—and led to a host of about-faces in previous medical beliefs. German researcher Robert Koch, often considered microbiology’s co-founder, then discovered the microbes that caused anthrax, cholera and tuberculosis. All cast aside earlier ideas. For instance, many in Koch’s Germany believed tuberculosis was a hereditary disease passed down through families until 1882, when the scientist unveiled Mycobacterium tuberculosis, the bacterium responsible for the disease.
While paradigm shifts in the physical and chemical sciences can greatly affect how technologies evolve in societally impactful ways, anything pertaining to the wellbeing of human bodies can easily become politicized. Mann offers examples pertaining to the decades long controversy over the age threshold recommended for regular breast cancer screenings and to the initial World Health Organization pronouncement in 2020 that COVID-19 could not be transmitted through the air. Government policies and mandates issued to thwart the COVID-19 pandemic were in part impelled by scientific understandings that were later overturned.

=== Copernican Revolution ===