It is well known that Harvey was influenced by Aristotle. This paper seeks to show that Harvey's quantitative argument for the circulation and his analogy of the heart with a pump do not go beyond Aristotle and may even have been inspired by passages in Aristotle. It also considers the fact that Harvey gives much greater prominence to a macrocosm/microcosm analogy between the weather cycle and the circulation of the blood than he does to the pump analogy. This analogy is (...) prominent in both the preface to the king and pivotal chapter eight of De Motu Cordis, and may indicate a significant influence from the Renaissance natural magic tradition. The full implications of this analogy are critical for Harvey's conception of the nature of the circulation, especially the constant interconversion of venous and arterial blood and the passage of blood through the lungs. The tendency to assume that Harvey had a superior method since he made such an important discovery may have led not only to overestimation of the influence from the new science of the seventeenth century, but also to underestimation of influence from the magical tradition. (shrink)