This paper concerns Aristotle and Galen’s scientific method and the place of philosophy in their natural scientific endeavors as manifested in their discussions on the role of the heart in the formation of the embryo. I will begin first by discussing Aristotle’s conception of natural sciences and his discussion on the role of the heart in the body and embryo. Following this is Galen’s critique of the role of the heart in the formation of the embryo. Galen had considerably more knowledge about anatomy and the construction of the embryo, yet his scientific method is not radically different from Aristotle’s as he also utilizes both logical arguments and observational data. Nevertheless, he attempts to banish philosophers from discussing anatomical issues, thus opening the path to specialization.