The Notebooks of Leonardo da Vinci

with any degree of certainty or even probability, and the testimony of contemporary records, however credulously interpreted, does not do more than double or triple that number. How he occupied his time would be a mystery if not for the existence of the vast collection of drawings, and particularly of the notebooks. These number more than five thousand pages, the contents of which I have attempted to classify under some fifty headings. This classification is, as I know, rough and imperfect, which the almost infinite variety of the contents rendered nearly inevitable. For, of this man who produced a few works of art most divinely well, it may be said that he took all knowledge as his province, and that in his individual achievement he symbolizes the diversity of an era as fully as can be said of any man at any period in the world’s history. To one who has studied them intermittently for more than a quarter of a century, these manuscripts—the product of how many thousand hours of intellectual activity!—are the records of the working of perhaps the mightiest machine that has ever been a human brain: fragments of a larger purpose, charted, defined, and explored, but never fulfilled, of which the treatises containing the sum of his researches in anatomy, physiology, and geology form component parts—fragments of a vast encyclopedia of human knowledge.

What thinker has ever possessed the cosmic vision so persistently? He sought to establish the essential unity of structure in all living things: the earth as an organism with veins and arteries, and the body of a man as a model for that of the world. The perceptions of his brain are hardly, if at all, restricted by the limitations of time and place. At rare times, however, the personal note emerges, and moods of exultation or depression flash out their meaning in a phrase. The mood of the seer finds expression in fable or allegory, or in the series of ‘the Prophecies,’ revealing the depth of his biting humor and his power of analyzing the motives that guide human conduct, or in speculation regarding the results that would follow the possible extension of man’s power—in which time has confirmed his foresight and his foreboding.

The manuscripts are a nearly inexhaustible quarry in which the student of every phase of Leonardo’s mental activity will find material. They are of peculiar value for the biographer, both in their revelation of personality and in the manner in which they react on contemporary