§71. Empiricism Ancient and Modern
The genius of empiricism is to use perceptual appearances as instruments with which to colonize the imperceptible for cognition. The European experiment with this empiricism unfolds in two phases.
The first spans eight centuries between Alcmaeon and Galen, and includes Hippocrates, Democritus, and Epicurus. A second, modernizing phase runs from the introduction of Arabic medical philosophy in the thirteenth century, to the sixteenth-century recovery of Alexandrian medicine and mathematics, and the seventeenth-century consolidation of experiments as the leading method in natural philosophy.A fragment of Alcmaeon reads, “The brain provides us with perceptions of seeing and hearing and smelling: from these might come about memory and belief, but from memory and belief, if it has reached a state of rest, on the basis of these, knowledge comes about.” This resembles Aristotle’s later explanation, and Galen says the medical empiricists take exactly this line with the “experience” on which they rest medicine’s whole techne. The idea of medical empiricism is that all medically important knowledge arises with attentive, professional experience. Memory yields knowledge without passing through a syllogism. This knowledge is a confident expectation, not an inference or insight, and though certainly not Aristotelian science, it grew in boldness as faith in Aristotle waned.5
That first empiricism became the idea that knowledge of nature arises from experience, with scientific concepts no less than medical ones cast from sensible sources. While medical empiricism limited medical knowledge to experience, medical rationalism held superior treatment to require theoretical knowledge of invisible causes. Medical empiricists say doctors should not concern themselves professionally with such theories, disparaging invisible causes because they are impossible to act on.
Doctors can only act on what they perceive, and should respond to discernable symptoms alone, ignoring hypothetical signs of imponderable causes. As the Arab physicians said, it is unprofessionally risky. Theoreticians like Democritus might take a chance and conjure a cosmology, but physicians must not use their patients that way.Galen wanted to discover causes (reasons) without forsaking experience. For that we have to combine theory and experience artfully, technically, and that takes experience, which must be controlled or, as Galen said, qualified by a reasoned understanding, and eventually a hypothesis. To the medical rationalists he said, you are right—we must investigate the causes of disease, and to the empiricists he said, we can achieve the enhanced knowledge you doubt when experience is subject to methodical control. Make medical empiricism methodical, practice observation duly qualified, and we acquire the knowledge of causes rationalists want in a way that respects empirical scruple. We do not perceive the cause, which is invisible, but we observe signs and know, by experience-controlled inference, how to extract the identity of the cause from indications we observe.
The empirical tradition of antiquity was the principal alternative to the rationalism of classical philosophy and its schools. Plato and Aristotle wanted to throttle this empiricism, but their alternatives—Plato's idea of dialectic and Aristotle's episteme—were scientifically sterile. Not even Aristotle proved anything scientific by his standard, and in his actual scientific works he ignores his ideal for a fruitful empiricism.
This line of empirical philosophy disappeared when natural inquiry disappeared in late antiquity. It was in the inconspicuous form of jurisprudence and the new universities that Europe began to think empirically again. By the end of the seventeenth century, Aristotle was finally displaced from natural philosophy (itself newly liberated from the universities) by a new empiricism long in preparation.
The first challenge of European empiricism was to fit experiments to the Aristotelian canon of scientific demonstration. The effort occupied the phase from Grosseteste to Ockham, who proved that it was hopeless, inadvertently stimulating exploration of alternatives inthe work of Buridan, Oresme, the Merton scholars, and farsighted natural philosophers like Cusanus, Telesio, and Bruno. However, these predecessors stimulate Galileo less than did ideas he discovered in new editions of Alexandrian mathematics. Bacon, Gilbert, Harvey, Boyle, and Newton adjust medical and Epicurean empiricism for a natural philosophy that is not just empirical (inferring unseen causes from perceptible signs) but programmatically experimental. The result is a new natural philosophy built on the Hippocratic method of signs, Galen's method of qualified experience, and the analogical and inductive methods of Epicurean canonic.
A Hippocratic author reminds physicians that “to discover something that was unknown before and, once discovered, makes things better than if it had not been discovered, is the ambition and work of intelligence, as it is to bring to fruition something that was half completed.” This is a civilization-defining legacy of Greek medicine. One searches Plato and Aristotle in vain for this questing appetite for experience. In fact Aristotle denigrates it. The best activity is contemplating, not seeking, which is a laborious business more fit for slaves than a free and truth-loving mind.6
Readers of new editions of Hippocrates in the Renaissance rediscovered the dignity of inquiry, and newly appreciated the idea from Galen and Ibn Sina that medicine has a scientific pedigree unbeholden to Aristotle. The scientific quality of medicine was emphasized at the University of Padua, alma mater to leaders of the early scientific revolution. Medicine uniquely combines a respectable ancient claim to science with more unavoidable reality-testing than other ancient or medieval sciences. Lured by legends of potent secrets hidden in nature and experiment as the way to uncover them, ancient empirical traditions were revived, and one begins to read of Democritus almost as much as Aristotle.7