"Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason"

Leonardo da Vinci highlights the fundamental difference between how natural phenomena unfold and how human understanding advances. Nature, according to Leonardo, follows an inherent rational structure, its patterns and laws exist first, governing everything, but for us, these are often invisible and inscrutable until we witness their consequences. The manifestations of nature, observed through experience and experiment, are the endpoints, the visible outcomes of causes that were in effect long before we recognized them.

For human beings, knowledge does not begin with an innate understanding of universal principles; we start with our senses and experience, observing the world’s surface phenomena. From these initial observations, curiosity is sparked. We gather data, witness patterns, and notice anomalies, and from such experiences, we are driven to seek the principles behind them, to uncover the hidden “reason” or rationale structuring what we observe. This process stands in contrast to nature’s pathway. While nature begins its sequence of events guided by reason and only results in experience, humans must invert this route, rallying experience as the starting point for intellectual investigation.

Da Vinci’s perspective is deeply empirical and anticipates modern scientific method. It underscores the active role the observer must take: experimenting, noticing, questioning, and then, critically, analyzing. He insists upon the humility of our position, we cannot deduce truth purely by logical reasoning or theoretical supposition; rather, our reasoning must be constructed successive to, and grounded in, what we have witnessed.

This approach safeguards against dogmatism and presumption, emphasizing observation’s primacy and iterative reflection. It suggests knowledge is cumulative and contingent, built layer upon layer through cycles of experience interpreted by reason. Ultimately, Leonardo urges a discipline of thought, scientific in spirit, where curiosity and patient inquiry bridge the gap between what is evident to the senses and what is true in the order of nature itself.