Key Principle
Scientific progress is real but does not constitute movement toward a fixed truth. Kuhn imports Darwin's decisive move -- replacing teleology with selection -- into the philosophy of science. Just as biological evolution proceeds from primitive beginnings rather than toward a predetermined goal, scientific development evolves from prior paradigms without converging on a single correct representation of nature. Progress is measured by puzzle-solving capacity (number and precision of problems solved), not by proximity to "what is really there." This reframing preserves genuine progress while severing it from ontological convergence: "Nothing that has been or will be said makes it a process of evolution toward anything" (Ch. XIII).
Why This Matters
This is the book's philosophical capstone. Without it, every prior chapter -- incommensurability, paradigm-dependent perception, non-cumulative change -- looks like an argument against the reality of scientific progress, feeding the relativism that critics (and postmodern appropriators) attributed to Kuhn. The Darwinian analogy resolves the tension: incommensurability and non-cumulative change are expected features of an evolutionary process with no predetermined endpoint, not embarrassments for a theory of progress. Kuhn can say "I am a convinced believer in scientific progress" precisely because he has redefined progress in functional rather than representational terms. The cause-effect inversion -- "Does a field make progress because it is a science, or is it a science because it makes progress?" -- dissolves the apparent uniqueness of scientific progress by revealing it as partly an artifact of labeling.
Good Examples
- The Aristotle-Newton-Einstein test case: "In some important respects, Einstein's general theory of relativity is closer to Aristotle's than either of them is to Newton's" (Postscript). This single observation refutes linear ontological convergence. If science were converging on truth, later theories should always be closer to each other than to earlier ones. Einstein's restoration of space-time properties "not unlike those once attributed to the ether" shows the path is branching, not linear -- while instrumental progress (more puzzles solved more precisely) remains real.
- Painting as lost science: When representation was painting's shared goal, critics chronicled cumulative progress (foreshortening, chiaroscuro); Leonardo moved freely between art and science. Only when painting renounced representational goals did the art/science divide deepen. This shows that the appearance of progress depends on community consensus about goals, not on a uniquely truth-tracking method (Ch. XIII).
- The ratchet mechanism: Two conditions act as a non-return valve: (1) a new paradigm must resolve some outstanding problem no alternative can solve; (2) it must preserve most accumulated problem-solving ability. Together they guarantee net gain in solved problems across revolutions, even though each revolution imposes genuine losses -- banished problems, narrowed scope, attenuated cross-group communication (Ch. XIII).
Counterpoints
- Genuine losses accompany every revolution. Progress through revolutions is not cost-free. Each shift banishes some previously solved problems (phlogiston explained metallic similarity; Lavoisier could not), narrows scope through increased specialization, and reduces communication across subspecialties. Depth grows reliably; breadth grows only through proliferation of specialties, not expansion of any single specialty's scope (Ch. XIII).
- The victory-as-progress tautology. Kuhn acknowledges a structural guarantee: victors rewrite textbooks, renounce prior literature, and practitioners see history as linear progress "toward the present" -- partly because no alternative view is available within the field. The perception of progress is partly tautological. Kuhn insists the crucial difference from "might makes right" is that paradigm-choice authority is vested in the professional community, not political power (Ch. XIII).
- The residual question left open. Kuhn deliberately avoids truth-talk throughout the book and closes by acknowledging the unanswered question: "What must the world be like in order that man may know it?" He insists this question predates his essay and is compatible with his evolutionary view, but he does not answer it (Ch. XIII).
Key Quotes
"If we can learn to substitute evolution-from-what-we-do-know for evolution-toward-what-we-wish-to-know, a number of vexing problems may vanish in the process." -- Thomas S. Kuhn, Chapter XIII
"Does a field make progress because it is a science, or is it a science because it makes progress?" -- Thomas S. Kuhn, Chapter XIII
"There is no theory-independent way to reconstruct phrases like 'really there'; the notion of a match between the ontology of a theory and its 'real' counterpart in nature now seems to me illusive in principle." -- Thomas S. Kuhn, Postscript
"The scientific community is a supremely efficient instrument for maximizing the number and precision of the problems solved through paradigm change." -- Thomas S. Kuhn, Chapter XIII
Rules of Thumb
- When evaluating whether a field has "progressed," ask whether puzzle-solving capacity has increased -- not whether its ontology has converged on a fixed truth.
- Beware the cause-effect inversion: we tend to call "science" whatever progresses, then marvel that science progresses. The label tracks success, not method.
- The appearance of linear progress is produced by textbook rewriting and winner's history. Check whether the field's actual trajectory includes reversals (abandoned problems returning as central) before assuming convergence.
- Genuine losses (explanatory scope, cross-disciplinary communication) accompany genuine gains (precision, new predictions). Progress is net gain, not pure gain.
- The Darwinian analogy applies to paradigm selection: the meaningful question is never whether a paradigm is the best possible one, but whether it is the best available one in a particular historical situation.
Related References
- resolution-and-conversion - The mechanisms by which paradigm selection actually occurs
- exemplars-and-tacit-knowledge - How puzzle-solving capacity is transmitted and measured through exemplars
- rules-of-thumb - Practical diagnostics for recognizing progress vs. domain-shift