But his restless nature did not leave him long at this. Returning to Florence he competed with Michelangelo; yet the service of even his native city could not retain him. His fame had attracted the attention of a new patron of the arts, prince of the state which had conquered his first master. In this his last venture, he forsook Italy, only to die three years later at Amboise, in the castle of the French king. The inner nature of Leonardo remained as untouched by the men he encountered as by the events which were then stirring Europe. Alone, he influenced others, remaining the while a mystery to all. The most gifted of nations failed to understand the greatest of her sons. Isabella d'Este, the first lady of her time, seeking vainly to obtain some product of his brush, was told that his life was changeful and uncertain, that he lived for the day, intent only on his art. His own thoughts reveal him in another light. "I wish to work miracles," he wrote. And elsewhere he exclaimed, "Thou, O God, sellest us all benefits, at the cost of our toil.... As a day well spent makes sleep {xiii} seem pleasant, so a life well employed makes death pleasant. A life well spent is long." Leonardo's views of aesthetic are all important in his philosophy of life and art. The worker's thoughts on his craft are always of interest. They are doubly so when there is in them no trace of literary self-consciousness to blemish their expression. He recorded these thoughts at the instant of their birth, for a constant habit of observation and analysis had early developed with him into a second nature. His ideas were penned in the same fragmentary way as they presented themselves to his mind, perhaps with no intention of publishing them to the world. But his ideal of art depended intimately, none the less, on the system he had thrown out seemingly in so haphazard a manner. His method gives to his writings their only unity. It was more than a method: it was a permanent expression of his own life, which aided him to construct a philosophy of beauty characteristic of the new age. He had searched to find a scientific basis for art, and discovered it in the imitation of nature, based on rational experience. This idea was, in part, Aristotelian, imbibed with the spirit of the time; though in the ordinary acceptance of the word Leonardo was no scholar, least of all a humanist. His own innovation in aesthetic was in requiring a rational and critical experience as a necessary {xiv} foundation, the acquisition of which was to result from the permanent condition of the mind. He had trained his own faculties to critically observe all natural phenomena: first try by experience, and then demonstrate why such experiment is forced to operate in the way it does, was his advice. The eye, he gave as an instance, had been defined as one thing; by experience, he had found it to be another.