Is a common approach to knowledge about man and nature possible? With Leonardo da Vinci as our starting point we will explore this question. Leonardo was much more than a painter; he was a sharp observer of man and nature. What he saw (structures) and what he did (using his miraculous left hand as syntax) was translated into insights and methods of construction as recorded in his notes books. His view was holistic, as witnessed by his study of the eye; from the anatomy of the eye he proceeded outwards to a theory of perspective, and inwards to an understanding how perception and mind are grounded in the brain. In this we see similarities to current studies of language, mind and brain. It is possible to see a kind of proto-version of the art of mathematical modeling in Leonardo. This is a methodology of wide scope, extending far beyond physics and engineering. With a sufficiently broad understanding of the key concepts of structure, syntax and algorithms we have a method strong enough to allow for a common approach to knowledge of man and nature, to what there is and how we know.