Philosophy of Science

What distinguishes a scientific theory from a myth, an ideology, or a metaphysical system? Why do we accept as knowledge what physics tells us, but not what astrology — or psychoanalysis, at least in its more speculative form — claims? These questions, simple at first glance, opened in the twentieth century one of the most consequential debates in contemporary philosophy. Its two central figures — Karl Popper and Thomas Kuhn — formulated answers that, far from reconciling, redrew the landscape of epistemology. ...

Few philosophers can claim to have changed, so deliberately and programmatically, the very purpose of human knowledge. Francis Bacon (1561–1626) did not merely propose one philosophical theory among many: he conceived a total reform of learning, a project intended to replace the Aristotelian tradition with a new method capable of generating useful, verifiable, and progressive knowledge. The title of his magnum opus — Novum Organum (1620) — announces, right on its cover, the scale of the ambition: a new instrument of thought, designed to supplant Aristotle’s ancient Organon, which had governed Western logic for nearly two millennia. ...

Charles Sanders Peirce American logician, mathematician, philosopher, and scientist. Founder of pragmatism and modern semiotics. One of the most original minds in the history of philosophy, though neglected in his lifetime. His work profoundly influenced William James, John Dewey, and the entire analytic and continental tradition of the 20th century. Trained in chemistry at Harvard University and employed for decades by the U.S. Coast and Geodetic Survey, Peirce never secured a permanent academic post — due in part to personal difficulties and to the hostility of influential academic figures such as the astronomer Simon Newcomb; it was William James who, paradoxically, supported him in his years of hardship and became his greatest publicist. This institutional marginality did not prevent him from developing, across hundreds of unpublished manuscripts, a philosophical architecture of extraordinary depth: an original phenomenology, advanced formal logic, a comprehensive theory of signs, and an evolutionary metaphysics. ...

Galileo Galilei Born in Pisa in 1564, Galileo Galilei is often called the “father of modern science.” A professor of mathematics at Pisa and Padua, in 1609 he improved the newly invented telescope and turned it to the sky — with results that shook Aristotelian cosmology: mountains and craters on the Moon, four satellites orbiting Jupiter, the phases of Venus, spots on the Sun. The heavens, after all, were not the perfect, immutable realm they had been supposed to be. ...

Imre Lakatos Imre Lakatos was a Hungarian-British philosopher of science and mathematics, a professor at the London School of Economics and one of the central figures in the debate on scientific rationality during the 1960s and 1970s. His work seeks an intermediate position between Popper’s falsificationism and Kuhn’s historical account: against the idea that a single refutation overturns a theory, but also against the idea that scientific change is mere irrational “conversion”. Lakatos proposed that the unit of scientific appraisal is not the isolated theory but the research programme, judged over time by its capacity to anticipate novel facts. He was also an original philosopher of mathematics, showing in Proofs and Refutations that mathematical knowledge grows through a dynamic process of conjectures, proofs, and counterexamples rather than by pure, finished deduction. ...

Isaac Newton Born in England in 1643, Isaac Newton is regarded as the author of the greatest synthesis of the Scientific Revolution and one of the greatest geniuses in history. During the “miraculous years” of 1665–66, when the plague drove him from Cambridge to the countryside, he laid the foundations of three simultaneous revolutions: the infinitesimal calculus, the theory of colors, and the law of gravitation. A complex man, he also devoted himself, in secret, to alchemy and to heterodox theological studies. He was Master of the Mint and President of the Royal Society, and is buried in Westminster Abbey. ...

Johannes Kepler Born in Weil der Stadt, Germany, in 1571, Johannes Kepler was a fascinating spirit of transition: a devout Protestant, he studied theology at Tübingen but devoted his life to astronomy, convinced that to decipher the order of the heavens was to read the mind of God. He worked as assistant to the great observer Tycho Brahe in Prague and, on inheriting his data of the highest precision — especially on Mars — had at his disposal the material that would make his discoveries possible. ...

Karl Popper Austrian-British philosopher. Proposed falsificationism as a criterion for scientific demarcation and defended the open society against totalitarianism. Sharp critic of Marxism and historicism. Born in Vienna in 1902, Popper came of age in intellectual contact with the Vienna Circle — the group of philosophers and scientists who sought to ground knowledge in strict verificationist terms. Rather than joining their programme, however, he turned the question around: the central problem of epistemology is not how we confirm theories, but how we distinguish genuine science from pseudo-science. His answer, falsificationism, holds that the hallmark of a scientific theory is its refutability: a claim is scientific if and only if it is possible to conceive of an observation or experiment that could prove it wrong. This methodological reorientation, set out in The Logic of Scientific Discovery (1934), reshaped the foundations of twentieth-century philosophy of science. ...

Nicolaus Copernicus Born in Toruń, Poland, in 1473, Nicolaus Copernicus was a canon of Frombork cathedral and a man of the Renaissance: he studied in Kraków and in Italy (Bologna, Padua), devoting himself to law, medicine, and, above all, astronomy. Discreetly and prudently, over decades he matured an idea that would change the image of the world — and that he would publish only at the end of his life. ...

Paul Feyerabend Paul Feyerabend was an Austrian philosopher of science and one of the most provocative thinkers of the twentieth century. Trained in Vienna and based for decades at Berkeley, he began close to logical empiricism and to Popper’s critical rationalism — he even studied under Popper at the London School of Economics — before becoming one of his sharpest critics. His best-known work, Against Method (1975), defends epistemological anarchism: the thesis that there is no single, universal, ahistorical scientific method capable of explaining the success of science. Examining real episodes from the history of science, above all the case of Galileo, Feyerabend argues that progress has often required breaking the methodological rules then in force. His provocation became synonymous with a radical defence of pluralism and intellectual freedom against every dogmatism — including the scientific one. ...

Thomas Kuhn American historian and philosopher of science. The Structure of Scientific Revolutions (1962) completely transformed the understanding of scientific progress and introduced the concept of paradigm into global intellectual vocabulary. Born in Cincinnati, Ohio in 1922, Kuhn trained as a physicist at Harvard University. While preparing a history of science course for humanities students, he wrestled with Aristotelian theories of motion. The puzzle of why Aristotle — a remarkably acute thinker — had made what seemed like obvious errors from a Newtonian standpoint led Kuhn to realize that the standards of scientific rationality themselves change across historical periods. Rather than asking “who was right?”, he began asking “how does a scientific community come to see the world in a particular way?”. That question shaped all his subsequent work, culminating years later in the book that would redefine how philosophers, historians, and scientists understand science itself. ...

Whitehead Alfred North Whitehead (1861–1947) was born in Ramsgate, Kent, and built a career on both sides of the Atlantic. For decades he taught mathematics and logic at Trinity College, Cambridge and at University College London, before accepting — at the age of sixty-three — an invitation to join the philosophy faculty at Harvard, where he produced his most ambitious metaphysical work. This dual trajectory, from mathematical rigour to cosmological speculation, defines his philosophy in a singular way: process thought does not emerge from a break with science but from a sustained philosophical meditation on its foundations. ...