I appeal to your own eyes as my witness and judge.

This line encapsulates Harvey’s characteristic empiricism: rather than asking readers to accept authority or scholastic tradition, he urges them to verify his claims by direct observation. In Harvey’s work on the motion of the heart and the circulation of the blood, he repeatedly grounds argument in anatomy, vivisection, and visible phenomena—what can be seen, measured, and demonstrated. The appeal to “your own eyes” frames the reader as an active judge of evidence, implying that truth in natural philosophy should be publicly testable. It also functions rhetorically as a challenge to opponents: if they dispute him, they must dispute what observation shows, not merely what inherited doctrine asserts.