The function of the heart is not obvious.

It is widely believed that the function of the heart is obviously to pump blood. I argue here that it is not. The definition, presentation, and pathophysiological explanation of heart failure, as well as the measurement of cardiac dysfunction, are not as might be expected if the function of the heart was simply to pump blood. Far from being obvious, many central features of heart failure are still being investigated. This has important implications for philosophical debates about health and disease. According to naturalists like Christopher Boorse, medical practice is founded on a well-established body of physiological knowledge, which provides the one true account of the biological function of organs. On this naturalistic view, there should only be one account of the pathophysiology of heart failure in use in medical practice. This account of the pathophysiology of heart failure should be well-established, as opposed to uncertain. Medics should use this physiological knowledge to inform their clinical practice, and not vice versa. Clinical considerations, such as whether patients respond to therapy, should not inform debates about what the pathophysiology of heart failure is. I will show this is not the case. The handling of knowledge of the biological function of the heart in medical practice differs substantially from Boorse's account.