The Renaissance was a period dominated by the Aristotelian philosophy. Varchi, in the preface of second of his "Two lessons on painting and sculpture", says that science is “nothing more than the knowledge of the universal things, necessary and consequently eternal, obtained by demonstration”, and art is “the disposition to make involving a true course of reasoning”, following the definitions of Nicomachean Ethics. Toletus, in his "Commentary on Aristotle’s Physics", divides the philosophy into speculative, practical and productive, following the beginning of the sixth book of Metaphysics. However, instead of the higher value given to the vita contemplativa in the Antiquity still present in the Middle Ages, Renaissance men like Salutati and Manetti gave new values to the vita activa, and craftsmen-writers like Alberti, Ghiberti and Martini aimed to elevate the value of their knowledge and their own social status. Different from the unlettered craftsmen, the craftsman imagined by them was a sort of lettered man who could work from the knowledge of principles and was able to speak about them. However, the definitions and the organizations of knowledge of the ancient texts were well established and clear. Leonardo da Vinci tried to surpass them and tried to identify art and science. After his education at Verrocchio’s atelier, in Milan Leonardo began to study matters like optics, physics and anatomy. In the case of anatomy, Leonardo took a very distinctive path, separating himself progressively from the craftsmen and the physicians. Without the prejudices of the university professors, he did dissections, and for him the painter-anatomist had to know “the good draughtsmanship”, “the knowledge of perspective”, “the methods of geometrical demonstration and the method of calculation of the forces and power of the muscles”. Using his art of drawing, his experience of dissection and his knowledge of mechanics, he could recreate the human figure “without seeing the living [and] without error”. However, the definitions and the organizations of knowledge did not permit the synthesis Leonardo da Vinci was proposing. He did not have disciples as an anatomist. It is argued here that Leonardo da Vinci’s anatomical studies are products of an active view of life, but still facing the limits of the Aristotelian philosophy present in the Renaissance. The natural philosophy, part of the speculative branch of philosophy, could be aided by the arts, but not directly elaborated by them.