Progress and History

by Unknown

Such is the sequence of the most influential names at the turning-point of modern thought.

Galileo's work, his experiments with falling bodies and the revelations of his telescope, carried the strategic lines of Greek science across the frontiers of a New World, and Newton laid down the lines of permanent occupation and organized the conquest. Organization, the formation of a network of lines connected as a whole, and giving access to different parts of the world of experience, is perhaps the best image of the growth of science in the mind of mankind. It will be seen that it does not imply any exhaustion of the field, nor any identification of all knowledge with exact or systematic knowledge. The process is rather one of gradual penetration, the linking up and extension of the area of knowledge by well-defined and connected methods of thought. No all-embracing plan thought out beforehand by the first founders of science, or any of their successors, can be applied systematically to the whole range of our experience. It has not been so in the past; still less does it seem possible in the future. For the most part the discoverer works on steadily in his own plot, occupying the nearest places first, and observing here and there that one of his lines runs into some one else's. Every now and then a greater and more comprehensive mind appears, able to treat several systems as one whole, to survey a larger area and extend that empire of the mind which, as Bacon tells us, is nobler than any other.

Of such conquerors Newton was the greatest we have yet known, because he brought together into one system more and further-reaching lines of communication than any one else. He unified the forms of measurement which had previously been treated as the separate subjects of geometry, astronomy, and the newly-born science of dynamics. Celestial mechanics embraces all three, and is a fresh and decisive proof of the commanding influence of the heavenly bodies on human life and thought. Not by a horoscope, but by continued and systematic thought, humanity was unravelling its nature and destiny in the stars as well as in itself. These are the two approaches to perfect knowledge which are converging more and more closely in our own time. Newton's work was the longest step yet taken on the mechanical side, and we must complete our notice of it by the briefest possible reference to the later workers on the same line, before turning to the sciences of life which began their more systematic evolution with the discovery of Harvey, a contemporary of Newton.

The seventeenth century, with Descartes' application of algebra to geometry, and Newton's and Leibnitz's invention of the differential and integral calculus, improved our methods of calculation to such a point that summary methods of vastly greater comprehensiveness and elasticity can be applied to any problem of which the elements can be measured. The mere improvement in the method of describing the same things (cf. e.g. a geometrical problem as written down by Archimedes with any modern treatise) was in itself a revolution. But the new calculus went much farther. It enabled us to represent, in symbols which may be dealt with arithmetically, any form of regular movement.

As movement is universal, and the most obvious external manifestation of life itself, the hopes of a mathematical treatment of all phenomena are indefinitely enlarged, for all fresh laws or forms might conceivably be expressed as differential equations. So to the vision of a Poincaré the human power of prediction appears to have no assignable theoretical limit.

The seventeenth century which witnessed this momentous extension of mathematical methods, also contains the cognate foundation of scientific physics. Accurate measurement began to be applied to the phenomena of light and heat, the expansion of gases, the various changes in the forms of matter apart from life. The eighteenth century which continued this work, is also and most notably marked by the establishment of a scientific chemistry. In this again we see a further extension of accurate measurement: another order of things different in quality began to be treated by a quantitative analysis. Lavoisier's is the greatest name. He gave a clear and logical classification of the chemical elements then known, which served as useful a purpose in that science, as classificatory systems in botany and zoology have done in those cases. But the crucial step which established chemistry, a step also due to Lavoisier, was making the test of weight decisive. 'The balance was the ultima ratio of his laboratory.' His first principle was that the total weight of all the products of a chemical process must be exactly equal to the total weight of the substances used. From this, and rightly disregarding the supposed weight of heat, he could proceed to the discovery of the accurate proportions of the elements in all the compounds he was able to analyse.

Since then the process of mathematical synthesis in science has been carried many stages further. The exponents of this aspect of scientific progress, of whom we may take the late M. Henri Poincaré as the leading representative in our generation, are perfectly justified in treating this gradual mathematical unification of knowledge with pride and confidence. They have solid achievement on their side. It is through science of this kind that the idea of universal order has gained its sway in man's mind. The occasional attacks on scientific method, the talk one sometimes hears of 'breaking the fetters of Cartesian mechanics', seem to suggest that the great structure which Galileo, Newton, and Descartes founded is comparable to the false Aristotelianism which they destroyed. The suggestion is absurd: its chief excuse is the desire to defend the autonomy of the sciences of life, about which we have a word to say later on. But we must first complete our brief mention of the greatest stages on the mechanical side, of which a full and vivid account may be found in such a book as M. Poincaré's Science et Hypothèse.

Early in the nineteenth century a trio of discoverers, a Frenchman, a German, and an Englishman, established the theory of the conservation of energy. To the labours of Sadi Carnot, Mayer, and Joule is due our knowledge of the fact that heat which, as a supposed entity, had disturbed the physics and chemistry of the earlier centuries, was itself another form of mechanical energy and could be measured like the rest. Later in the century another capital step in synthesis was taken by the foundation of astrophysics, which rests on the identity of the physics and chemistry of the heavenly bodies with those of the earth.

The known universe thus becomes still more one. Later researches again, especially those of Maxwell, tend to the identification of light and heat with electricity, and in the last stage matter as a whole seems to be swallowed up in motion. It is found that similar equations will express all kinds of motion; that all are really various forms of the motion of something which the mind postulates as the thing in motion; we have in each case to deal with wave-movements of different length. The broad change, therefore, which has taken place since the mechanics of Newton is the advance from the consideration of masses to that of molecules of smaller and smaller size, and the truth of the former is not thereby invalidated. Newton, Descartes, Fresnel, Carnot, Joule, Mayer, Faraday, Helmholtz, Maxwell appear as one great succession of unifiers. All have been engaged in the same work of consolidating thought at the same time that they extended it. Their conceptions of force, mass, matter, ether, atom, molecule have provisional validity as the imagined objective substratum of our experience, and the fact that we analyse these conceptions still further and sometimes discard them, does not in any way invalidate the law or general form in which they have enabled us to sum up our experience and predict the future.

But now we turn to the other side. In spite of the continued progress noted on the mechanical side, it is true that the predominant scientific interest changed in the nineteenth century from mechanics to biology, from matter to life, from Newton to Darwin. Darwin was born in 1809, the year in which Lamarck, who invented the term biology, published his Philosophie Zoologique. The Origin of Species appeared in 1858 after the conservation of energy had been established, and the range and influence of evolutionary biology have grown ever since.