In the history of science there is a consistent antithesis between idealism and sensationalism. According to one school of historians (which, having the authority of Locke behind it, has flourished throughout the last two centuries), man’s conception of his natural environment is essentially formed through sensation: of course, the senses unaided brought man little knowledge, and during the period in which he relied on them alone science was necessarily speculative, even magical, certainly restricted. Richness and precision of knowledge can come only from a great number of carefully specified sensations (colored patches, meter-readings, geometric tracings) such as experimental investigation provides. So knowledge, it is held, has developed—that is, approximated to what we now believe to be knowledge—in proportion to the quantity and quality of organized sensation, in other words empirical data.

Sensationalist historians of science do not deny the scientist’s cerebral functions for the data as they accumulate present ever new and hardier puzzles in their classification and interpretation; what they assert is the primacy of sensation (data) over cerebration. Their position has an obvious Lockean plausibility. Surely, before thinking, one must single out phenomena to think about? And are there not many examples—like Becquerel’s accidental discovery of radioactivity—of the unpredictable fact serving as nucleus for a fresh complex of theoretical activity?

The idealist historian of science cannot doubt the occurrence of accidents. What he opposes is the conception of the human mind as an empty storeroom gradually filled up with packages of facts neatly stacked into theoretical patterns. Rather the idealist sees knowledge as a picture of the external world painted by the mind; the function of cerebration is to criticize and modify this picture in order to render it as complete and brilliant as possible. Sensation is the intermediary between this picture and reality (which is, it goes without saying, unknowable, a truth which even the empiricist admits); therefore empirical data enter into the composition of the picture, but cannot dominate its composition, which is the work of thought.

Scientific empiricism has been traditionally English; scientific idealism traditionally French, from Descartes to Poincaré. Alexandre Koyré (1892-1964), the most fervent idealist among historians of science in recent times, was a Parisian of Russian birth. Born at Taganrog, educated at Tiflis and Rostov-on-Don, he moved from there to Göttingen and the Sorbonne. In the later years of his life he was also a staff member of the Institute for Advanced Study at Princeton. His early work was on mathematics and philosophy, from Russell’s numbers to Anselm’s God, and it was not until 1937 that he turned his attention to history with an essay on Galileo and the famous experiment at the Leaning Tower of Pisa, which he proclaimed a fiction. Two years later appeared a classical monograph, Etudes Galiléennes. When, after the war, this book, along with Koyré’s later writings (some published in the Journal of the History of Ideas), became better known in the United States, it was evident that a new, major force was at work. In the twenty years remaining, he produced further studies of seventeenth-century science, on Galileo again, Mersenne, Kepler, Borelli, and, especially, Newton, and was acknowledged as a leading figure in the history of science.

Koyré’s range was limited. He did not trespass outside the Renaissance and seventeenth century, nor beyond mechanics and astronomy. He was little interested in any of the processes by which the facts of nature are ascertained, preferring to trace the tortuous paths by which men form theoretical views, and to justify them. In the opening paragraph of “Galileo and the Scientific Revolution” in Metaphysics and Measurement, he wrote:

there is nothing more interesting, more instructive, nor more thrilling, than to study the history of that effort [the scientific revolution]; to write the story of the human mind dealing obstinately with the same everlasting problems, encountering the same difficulties, struggling untiringly with the same obstacles, and slowly and progressively forging for itself new instruments and tools, new concepts, new methods of thinking, which will enable it to overcome them.

The sensationalist dwells on the novel facts that reshape problems; Koyré was interested in the new thought that solves man’s perpetual questions. His tool was the meticulous and wonderfully intelligent analysis of original texts, often of a single book.

THE PAPERS and essays reproduced in both these collections of Koyré’s shorter writings are concerned with the scientific revolution,

one of the profoundest, if not the most profound, revolutions of human thought since the invention of the Cosmos by Greek thought: a revolution which implies a radical intellectual “mutation,” of which modern physical science is at once the expression and the fruit.

Galileo was, in Koyré’s mind, the prime revolutionary. In the essay on Galileo and Plato (1940) he rejected the view that modern science was inaugurated in the Middle Ages:


The true forerunner of modern physics is neither Buridan, nor Nicole Oresme, nor even John Philoponos, but Archimedes.

Though in later years he saw more significance in the history of late medieval physics, he could find in it at best only the preparation for modern science. The reason for this is clear. Modern physics is a mathematical science, it begins with the “geometrization of nature.” Medieval science employed calculation, but it was not mathematical; it was Aristotelian, not Platonic. Galileo was the transcendant Platonist, in the sense that one who “claims for mathematics a superior value, and a commanding position in the study of things natural…is a Platonist.” Moreover, Galileo was a leader in the destruction of the Greek Cosmos, with its hierarchical order and opposition of Heaven and Earth; the destruction of one world and its replacement by another was a conceptual change, a reshaping of “the framework of our intellect itself.” Galileo was also the founder of the fundamental modern science, mechanics.

To Koyré it was clear that the inauguration of modern science was the work of the philosophic intellect of such men as Galileo and Kepler (it is a pity that Koyré’s studies of Kepler are not better represented in these volumes). It was not the work of humanism, nor any other mysterious shift in the human spirit, nor the result of a struggle against authority. Least of all was it the fruit of “brute, commonsense experience” which, if anything, played a negative, obstructive role. Two of his best papers argue that two experiments claimed by Galileo did not take place as Galileo described them, including the marvelous precision obtained by rolling balls down an inclined plane. In one of these papers, he concludes:

We know quite well that Galileo was right. Good physics is made a priori

and the second echoes it:

not only are good experiments based upon theory, but even the means to perform them are nothing else than theory incarnate.

Such extreme idealism has not been without its critics. Galileo’s experimental technique has been vindicated by repetition; one can point also to his immense care, and success, in telescopic observation. But I do not think that Koyré meant to teach that all science is done in the study, and not at the bench, observatory, or microscope:

Naturally, there is no question of neglecting, or minimizing, the part played by experiment. It is obvious that experiment alone can provide the numerical data without which our knowledge of nature remains incomplete and imperfect.

Of course Koyré understood very well the simple point of logic that scientific truths are not formal but contingent. I doubt if this interested him much; he wanted to know how men attain truth, not how exactly they demonstrate it. What he really opposed—as Darwin opposed it—was the notion that encyclopaedias full of data taxonomically arranged could ever of themselves generate a new idea.

Koyré’s studies of the creators of the scientific revolution during the first half of the seventeenth century is, in my opinion, his most important contribution to the history of science. His work on Newton, although technically superb and a brilliant intellectual achievement, has not quite the same transforming power. Yet Koyré was the unquestioned leader among Newtonian scholars. His early paper (1948) on “The Significance of the Newtonian Synthesis” in Newtonian Studies is still an admirable general essay. The same collection contains one of his best essays, “An Unpublished Letter of Robert Hooke to Isaac Newton,” distinguished by its scholarship, wit, and depth of insight; yet it was written in 1952, before he had discovered the riches of the Newton manuscripts in Cambridge. There was a logic in his life that led Koyré toward the end to the painful collation of manuscripts—the philosopher cheerfully taking on the historian’s drudgery—for Newton was Koyré’s terminal point; he did not look beyond. (Not that he idolized Newton; no one was more keenly aware of Newton’s limitations as man, metaphysician, and theologian.) He submitted to the fascination of exploring line by line, revision by revision, the detailed operations of one of the greatest of minds. But the result was that Koyré, in ceasing to write about the history of physics, wrote about an individual physicist. When he explored the work of Kepler, Galileo, Borelli, one could say “This is the mind of the scientific revolution at work.” But Newton’s mind was a phenomenon apart. As Koyré pointed out in the essay, “Attraction, Newton, and Cotes,” reprinted here, even so close a colleague as the editor of the second edition of the Principia could fail to follow the inner workings of Newton’s thought. In the eighteenth century “Newtonianism” became something that Newton himself would hardly have recognized.


As is evident from the earlier book, From the Closed World to the Infinite Universe, Alexandre Koyré cut cleanly through layers of misunderstanding to reveal that Newton’s idea of nature contained strong traces of metaphysical and religious influences. He showed in the earlier book how Newton was influenced by the philosophy of Henry More; in the later Newtonian Studies there is a previously unpublished study of Newton and Descartes, more than sixty pages long and followed by eighty pages of appendices! The message in this essay too is that “Newton’s thought, nearly ab ovo, had been formed and developed in opposition to that of Descartes.” It was an opposition that led Newton to anti-mechanism, to a denial of the absolute existence of matter, and to a conception of immanent deity. As Koyré remarks, the road to truth is far from straight: Newtonian physics was itself a religious protest against Cartesian metaphysics.

Those pieces originally written in French have been ably translated by Dr. R. E. W. Maddison. Both collections contain much of Koyré’s best historical writing as well as evidence of his weaknesses. He has had a tremendous and beneficial influence in the United States and Britain, though less in France where, perhaps, his style of history seemed less new. (Had Koyré written only in French, would this have happened?) No one reading him can doubt his immense learning or his passionate respect for human intelligence. He detested any suggestion that chance or mere mechanical drudgery could take the place of intellect.

The idea that in the history of science one should look for the traces of the working mind has had catalytic value, although Koyré, the philosopher, was by no means alone in his idea, for he had been preceded by Burtt and Lovejoy working along different lines. Koyré himself knew, however, that the applications of his idea are restricted. In the history of science places must be found for the accidental and the plodding, and in Koyré’s last and best book, La Révolution Astronomique, there is some hint of this, particularly in his study of Kepler. Sheer mathematical virtuosity and depth are first essentials for creation in the kind of science that Koyré loved to study; he knew this, but he preferred to take it for granted rather than to work out its historical complexity. The “geometrization of nature” was less a process than a concept. One may feel, sometimes, that Koyré’s fine-spun reconstructions verge on the tenuous, or that, after all, few human beings live on the exalted planes of intellect to which Koyré pursued his subject. What those who learned from him recall, however, and try to imitate, is his profound faith in the power and honesty of human reason.

This Issue

August 1, 1968