Philosophy of science

Philosophy and natural science

The history of philosophy is intertwined with the history of the natural sciences. Long before the 19th century, when the term science began to be used with its modern meaning, those who are now counted among the major figures in the history of Western philosophy were often equally famous for their contributions to “natural philosophy,” the bundle of inquiries now designated as sciences. Aristotle (384–322 bce) was the first great biologist; René Descartes (1596–1650) formulated analytic geometry (“Cartesian geometry”) and discovered the laws of the reflection and refraction of light; Gottfried Wilhelm Leibniz (1646–1716) laid claim to priority in the invention of the calculus; and Immanuel Kant (1724–1804) offered the basis of a still-current hypothesis regarding the formation of the solar system (the Kant-Laplace nebular hypothesis).

In reflecting on human knowledge, the great philosophers also offered accounts of the aims and methods of the sciences, ranging from Aristotle’s studies in logic through the proposals of Francis Bacon (1561–1626) and Descartes, which were instrumental in shaping 17th-century science. They were joined in these reflections by the most eminent natural scientists. Galileo (1564–1642) supplemented his arguments about the motions of earthly and heavenly bodies with claims about the roles of mathematics and experiment in discovering facts about nature. Similarly, the account given by Isaac Newton (1642–1727) of his system of the natural world is punctuated by a defense of his methods and an outline of a positive program for scientific inquiry. Antoine-Laurent Lavoisier (1743–94), James Clerk Maxwell (1831–79), Charles Darwin (1809–82), and Albert Einstein (1879–1955) all continued this tradition, offering their own insights into the character of the scientific enterprise.

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Although it may sometimes be difficult to decide whether to classify an older figure as a philosopher or a scientist—and, indeed, the archaic “natural philosopher” may sometimes seem to provide a good compromise—since the early 20th century, philosophy of science has been more self-conscious about its proper role. Some philosophers continue to work on problems that are continuous with the natural sciences, exploring, for example, the character of space and time or the fundamental features of life. They contribute to the philosophy of the special sciences, a field with a long tradition of distinguished work in the philosophy of physics and with more-recent contributions in the philosophy of biology and the philosophy of psychology and neuroscience (see mind, philosophy of). General philosophy of science, by contrast, seeks to illuminate broad features of the sciences, continuing the inquiries begun in Aristotle’s discussions of logic and method. This is the topic of the present article.

Logical positivism and logical empiricism

A series of developments in early 20th-century philosophy made the general philosophy of science central to philosophy in the English-speaking world. Inspired by the articulation of mathematical logic, or formal logic, in the work of the philosophers Gottlob Frege (1848–1925) and Bertrand Russell (1872–1970) and the mathematician David Hilbert (1862–1943), a group of European philosophers known as the Vienna Circle attempted to diagnose the difference between the inconclusive debates that mark the history of philosophy and the firm accomplishments of the sciences they admired. They offered criteria of meaningfulness, or “cognitive significance,” aiming to demonstrate that traditional philosophical questions (and their proposed answers) are meaningless. The correct task of philosophy, they suggested, is to formulate a “logic of the sciences” that would be analogous to the logic of pure mathematics formulated by Frege, Russell, and Hilbert. In the light of logic, they thought, genuinely fruitful inquiries could be freed from the encumbrances of traditional philosophy.

To carry through this bold program, a sharp criterion of meaningfulness was required. Unfortunately, as they tried to use the tools of mathematical logic to specify the criterion, the logical positivists (as they came to be known) encountered unexpected difficulties. Again and again, promising proposals were either so lax that they allowed the cloudiest pronouncements of traditional metaphysics to count as meaningful, or so restrictive that they excluded the most cherished hypotheses of the sciences (see verifiability principle). Faced with these discouraging results, logical positivism evolved into a more moderate movement, logical empiricism. (Many historians of philosophy treat this movement as a late version of logical positivism and accordingly do not refer to it by any distinct name.) Logical empiricists took as central the task of understanding the distinctive virtues of the natural sciences. In effect, they proposed that the search for a theory of scientific method— undertaken by Aristotle, Bacon, Descartes, and others—could be carried out more thoroughly with the tools of mathematical logic. Not only did they see a theory of scientific method as central to philosophy, but they also viewed that theory as valuable for aspiring areas of inquiry in which an explicit understanding of method might resolve debates and clear away confusions. Their agenda was deeply influential in subsequent philosophy of science.