LEONARDO DA VINCI

Every generation either constructs a new periodization of the past or puts a different emphasis upon the periodization it has inherited. At the end of the twentieth century we have come to speak of a "scientific revolution," dated roughly between 1550 and 1700. We commonly regard this revolution as the greatest change of direction in the history of western civilization since the birth of Christianity.

In spite of the persistence of cultural patterns stemming ultimately from the Greeks and the Hebrews, we realize that the society which emerged from the scientific revolution was profoundly different from what had gone before. The work of Copernicus and Kepler, of Galileo, Descartes and Newton created a new world. For this reason increasing effort has been directed to the understanding of the immediate background of this revolution, that is, the history of scientific thought in the period of the later Middle Ages and the Renaissance.

During the course of the l4th century there had been elaborated at the Paris school an attack on the Aristotelian theory of motion. Aristotle's physics had assumed that bodies in their natural state were at rest and that what required explanation was motion. Consequently there had been the conception of the prime mover and, where the agent of motion was not obvious, this had to be invoked. In the case of projectiles the assumption was that they were carried along by the push of air. Now the critics of this theory among the 14th-century scholastics had developed an analysis of what they called impetus, a quality supposed to have been assumed by the projectile which carried it along in its flight. This was a stage on the way toward the modern theory of inertia, not finally developed until the l7th century.

This work of the Paris school was assimilated and developed particularly at Padua in the l5th and l6th centuries. The University of Padua was celebrated as the center of medical studies, and the home of a most persistent Aristotelian tradition. In particular the doctrines of Averroes, the celebrated Arabic commentator of Aristotle, attained there an enormous influence, reflected in many ways in the science and philosophy of the whole Italian Renaissance. Working on these materials, the scholars of Padua made important contributions to he evolution of scientific method by applying themselves to he constant and rigid critique of the traditional scholastic problems. This work of the Paduan school was eclipsed and misunderstood because of the attacks of the humanists in the l5th and l6th centuries. The philosophical and grammatical interests of the humanists, and their eagerness to attain a greater place in education for their discipline, led them to despise the traditional subjects of university instruction.

Humanistic literature contains a long series of diatribes against science and scholastic logic. In spite of these attacks, however, the current of Aristotelian thinking persisted and made indispensable contributions to the development of scientific ideas, particularly on the subject of he theory of motion. The recognition of she historical importance of the school of Padua has thus finally provided an effective answer to those who condemned the sterility of the traditional debates in the name of a higher educational interest.

The humanist contribution to the emergence of new scientific thinking may be summarized under two heads. It was in part a contribution to methods and in part an addition to a specific body of knowledge, chiefly about ancient science. The critical scholarship of the humanists, although. devoted almost exclusively to the explanation of classical texts, must clearly have had an effect on other areas of thought. The painstaking research into the history of a text, the insistence on accuracy, the ideals of critical scholarship, connected as they were with a growing sense of history, could not but produce an alteration in the general intellectual climate.

Furthermore, the interests of the humanist in a set of simple general ideas, derived from research into the meaning of, a particular author, offered a striking contrast to the typical scholastic commentary cluttered with an infinity of detail. The broad lines, for example, of Erasmus interpretation of the meaning of the Pauline Epistles, as contrasted with the Sentences of Peter Lombard, might have suggested a similar simplicity and directness of approach in dealing with problems in quite a different area. Although it is very difficult to document the humanist influence in this respect, it is clearly not possible to neglect it altogether.

Far more obviously and directly important was the provision by the humanists of a body of texts and translations of Greek science and philosophy. The translations into Latin of Ptolemy, Archimedes, Galen, and others were landmarks in the history of western scientific thought. Those Greek works which were strictly scientific stimulated a new insight into the possibility of the investigation of the physical world. The Platonic revival, on the other hand, disposed men to think about the universe in terms of simple mathematical harmonies, and the combining of these two parts of the Greek inheritance had effects in both the arts and sciences, in the development of perspective, as well as the theories of human proportion, in architecture and in astronomy and cosmography.

The preponderance of one or another of these influences on the formation of Leonardo's genius has been debated. It has been maintained, for example, that Leonardo was saved by his ignorance and that his achievements in practical and theoretical science were possible only because he was spared subjection to be dogmatism of the formal scholastic tradition in the university. It is true that he was apprenticed to he studio of Verrocchio at an early age, when he had only the minimum of a formal education, and he was therefore perhaps left more free to follow the bent of his curiosity unhampered by the learning which fashioned so many of his contemporaries.

On the other hand, however little formal education Leonardo had received, by the tie he entered Verrocchio's studio he was already acquainted with Toscanelli, the famous Florentine scientist and presumed correspondent of Columbus. Toscanelli undoubtedly fostered his interest in physics. Leonardo also attended the lectures of the Greek exile, Argyropoulos, who introduced him to the humanistic texts and especially to the Greek philosophic and scientific traditions. Clearly, even if we are to attempt to explain Leonardo on the grounds of his fortunate escape from a university education, the importance of both humanist and scholastic learning cannot be minimized.

With these beginnings Leonardo continued throughout his life to display an enormous range of interest in scientific and philosophical problems, although there were very few subjects either of theoretical or practical character the investigation of which he carried to a logical conclusion. The product of these interests consisted of the famous hundred and twenty notebooks which he bequeathed to his friend, Francesco de Melzi. Of these hundred and twenty notebooks only a part now remains, dispersed in various museums and libraries in Europe. From these fragments it is extraordinarily difficult to derive any coherent idea of what Leonardo's purpose was and what shape these volumes were ultimately to assume in his mind.

Was this mass of notes intended to be ordered in a series of treatises on separate important subjects, or was it intended as a basis for a kind of summa on the current state of human knowledge about the universe? From the scanty indications we have it is impossible to tell. Clearly these notes as they exist were not intended for publication. Leonardo did not write in Latin but in a difficult Italian, complicated further by the fact that he used mirror-writing and wrote in reverse from right to left. Most of the manuscripts that survive date from beginning of the l6th century and do not include any of his notes before 1500.

A great deal has been made of the few remarks in Leonardo's manuscripts about the importance of following experience as opposed to theory. Clearly there were areas in which Leonardo followed this precept constantly and some of his insights, built on actual observation, do in fact anticipate the interests and achievements of a much later generation. This is particularly true of the problem of fossil shells found in she mountains far from the sea. It has been claimed that with his theoretical analysis of this subject Leonardo founded the science of paleontology. All his work on anatomy was also clearly founded on daily and painstaking observation.

Some of the notes comprise a careful record of dissections, which were the basis of his accounts of human anatomy. Furthermore, in the practical engineering problems in which he interested himself, particularly his strange and long-continued absorption in the problem of constructing a flying machine nod his investigation of the possibility of supporting underneath the water a submarine diver who would be constantly supplied with air, we have examples of the application of scientific observation of the sort that have been familiar to us since the period when the achievements of natural science began to dominate European intellectual history.

On the other hand, against these examples of the use of observation and the practical application of theory it must be said that large amounts of material in the notebooks are nothing more than digests of medieval scientific treatises, many conclusions of which were accepted by Leonardo in a completely uncritical and unscientific manner. His anatomical work led him to the very threshold of discovering the circulation of the blood, which he would have done except for his acceptance of Galen's theory of the invisible pores in the inner walls of the heart. Here then we have not the result of observation, but an example of the obstructive action of authority. Altogether we must conclude that Leonardo's scientific work, remarkable as it is in many ways, was not quite so unique as it has sometimes been represented to be. With Leonardo we are only partly on the way to the divorce between magic and the experimental method and the connection of the latter with natural science which was to be achieved in the l7th century, when the modern era in fact began.

In that progress it may perhaps be maintained that Leonardo's practical achievements were more important than his theoretical innovations. His preoccupation with feats of engineering like the flying machine, the control of the water supply, the construction of engines of war, represent tic exploration of sources of power which became the central characteristic of western technology. Such practical applications were a constant stimulus ha she formulation of new theoretical problems.

The very multiplicity of the interests which Leonardo represented is commentary on how little either his thought or his action was compartmentalized into those divisions which have become so characteristic of the modern world. The man who more than any other single figure has seemed to successive generations to be a microcosm of the creative forces of his age, the archetype of universal man, was at once scientist and artist, theorist and practitioner. He stood at a critical point when the great lines of division were beginning. The arts were ceasing to be crafts and were becoming "fine arts." The opposition between the world of science and the world of art was becoming discernible. The theorist was coming to be separated from the practical worker. Yet for Leonardo these dichotomies did not exist. The highest achievements of art could be determined by scientific rules, on the proportions of the human body, on perspective, on effects of light and shadow. Like those of his contemporaries who were concerned with harmonizing the historical religions and philosophic traditions, Leonardo perceived behind the apparent multiplicity of the universe a single truth.