1. Introduction

Leonardo da Vinci (1452-1519) has evoked two fundamentally different responses: one sees him as central to early modern science, another dismisses him as an eccentric with no influence. Both views were found while he was still alive. For instance, Pacioli (1509) praised him as being among the most perspicacious of architects and engineers, an assiduous inventor of new things, famous for sculpture and painting, for his construction of the horse, the Last Supper and for his writings: that he was working on "an inestimable work on local motion, percussion, weights and all the forces, that is, accidental weights, having already with great diligence finished a worthy book on painting and human movements."^[1] Aspects of this view were kept alive by Venturi (1797)^[2], Solmi (1905)^[3], Uccelli (1940)^[4], Reti (1974)^[5] and Keele.^[6] On the other hand, Castiglione (1528)^[7] criticized him indirectly for frittering away his time on useless mathematical speculation. Serlio (1545) made a different claim: that Leonardo was too much of a perfectionist and that this kept him from publishing.^[8]

Twentieth century scholars such as Marie Boas Hall argued that because he never published he had no influence^[9], while one recent scholar has dismissed him as "an ingenious empiricist working in an intellectual vacuum."^[10] Was Leonardo merely a recluse working on his own out of touch with the great traditions; an over ambitious amateur making notes without any underlying method and structure? This paper shows that Leonardo was widely read and in contact with some of the major scholars of his day. A survey is made of his extant treatises to confirm that these are much more structured than is at first apparent. His plans for books are examined to discern how he intended to arrange his material. It is shown that for all his universality Leonardo focussed on a surprisingly small number of basic themes; that although Leonardo's study of the natural world includes physics, biology and botany he treats them all in terms of mechanics. A detailed reading of his notebooks reveals that he was guided (and inevitably sometimes misguided) by a clear method. The notebooks also contain proof that Leonardo did not write them solely for private study; that he specifically intended them for other readers and had plans for publication. Finally, it will require a survey of historiography to understand how all all this could have been forgotten, with the result that scholars have claimed that he was a peripheral figure, when in fact Leonardo's method is of central importance to the western tradition.