A modern reader of Harvey's most famous and important work, "On the Motion of the Heart and Blood in Animals," cannot help but be amazed at the methodical, precise way he goes about demonstrating his thesis. His method is not purely "scientific" in the sense we know it today, but it does represent a great step toward the scientific method. Harvey himself would disagree on this point--he viewed the then-current crop of scientific theorists (Descartes, Bacon, et al.) with disdain. He considered himself a philosopher, and judging by his remarkable adherence to Aristotelian principles, one might be willing to grant him that. History, of course, has judged him to be a scientist and a physician, however, and we have learned to think of him exclusively in those terms. Not that this is a negative or even largely incorrect judgement; it just fails to take into account the full extent of William Harvey the man, and his motivations for inquiry. I think the only proper way to view him is as a transition point between Aristotelian natural philosophy and the scientific method. This book is a remarkable document because it is both a crucial turning point in the history of ideas and proof that those ideas were not so far apart as we have been led to believe.