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August 28, 2007
On Circulation and Truth
Why is it that for nearly 1300 years intelligent doctors and philosophers followed Galen's very bizarre misunderstanding of the function of the heart and the blood. Why did everyone believe Galen (and his view was an improvement over the previous five hundred years)?
People had obviously looked at hearts from the time of Moses at least, and probably from Abel. But Galen decided from his otherwise very careful observations (this was a fellow who could do cataract surgery among others) that the venous and arterial systems were unconnected, that the spirit principle entered the lung and thus the blood and somehow diffused through pores in the septum of the heart to join the vital principle coming from the liver, which generated the blood for the rest of the body, where it was consumed. There is evidence that Galen even recognized the pump function of the heart. (The heart valves were discovered by Erasistratus around 300 years before Christ, or nearly 500 years before Galen. Galen knows there is evidence for a one way flow, and he knows these arguments for the pump feature. He corrects the very mistaken notion that the vessels are full of air.)
His inability to see the capillaries should not have prevented him from making the simple calculation that Harvey later made of the untenable quantity of blood consumed each day under his theory.
It has been argued that Galen's desire to vindicate Plato's view of the soul against the Stoics blinded him to the obvious conclusions of his observations.
What explains the ensuing 1300 years of willful blindness? (There might have been a Muslim, Ibn Al-Nafis, who discovered the pulmonary circulation a few hundred years prior to Harvey, being uninhibited by the Greek philosophical arguments.) There was certainly there was much distraction from investigation. The prohibitions against dissection existed in Rome as well as in the church, so it wasn't just that, though the prohibition may have meant more to Christians for different reasons. (Vivisection of animals was at least discouraged by the church, if not fully prohibited at times. This was a important part of Harvey's experiments.) Basically, I think there was no incentive theologically to change the view.
It has been argued that lack of accurate experimentation is what kept first Erasistratus, then Galen, then Spieghel, from drawing accurate conclusions. Granted that these men did not have all the tools, or all the colleagues competing, or all the previous knowledge and successes to build on. Nonetheless, they were incredible observers, great theorists, insightful concluders. Except when their assumptions were wrong.
So what looks like the accurate scientific explanation might not be,
even if it held for 1400 years. And wrong interpretations flow from
wrong presuppositions, theological ones.
| By Robert Maddox | 03:33 PM