The Story of Western Science

by Susan Wise Bauer

  MAJOR PREMISE: All heavy matter falls toward the center of the universe.

  MINOR PREMISE: The earth is made of heavy matter.

  MINOR PREMISE: The earth is not falling.

  CONCLUSION: The earth must already be at the center of the universe.

  But Bacon had come to believe that deductive reasoning was a dead end that distorted evidence: “Having first determined the question according to his will,” he objected, “man then resorts to experience, and bending her to conformity with his placets [expressions of assent], leads her about like a captive in a procession.” Instead, he argued, the careful thinker must reason the other way around: starting from specifics and building toward general conclusions, beginning with particular pieces of evidence and working, inductively, toward broader assertions.4

  This new way of thinking—inductive reasoning—had three steps to it. The “true method,” Bacon explained,

  first lights the candle, and then by means of the candle shows the way; commencing as it does with experience duly ordered and digested, not bungling or erratic, and from it deducing axioms, and from established axioms again new experiments.

  In other words, the natural philosopher must first come up with an idea about how the world works: “lighting the candle.” Second, he must test the idea against physical reality, against “experience duly ordered”—both observations of the world around him and carefully designed experiments. Only then, as a last step, should he “deduce axioms,” coming up with a theory that could be claimed to carry truth.5

  Hypothesis, experiment, conclusion: Bacon had just traced the outlines of the scientific method.

  It was not, of course, fully developed. But Part II of Bacon’s Great Instauration was a clear challenge to the deductive thinking of the Aristotelian corpus. Bacon even named it Novum organum (“New Tools”), after Aristotle’s logical treatises titled Organon. On the cover of the Novum organum, Bacon placed a ship—his new inductive method—sailing triumphantly past the Pillars of Hercules, the mythological pillars that marked the farthest reach of Hercules’s journey to the “far west.” Identified by most ancient authors as the promontories on either side of the Strait of Gibraltar, the Pillars represented the outermost boundaries of the ancient world, the greatest extent of the old way of knowledge.6

  Barely a year after publication of the Novum organum, Francis Bacon was accused by his enemies at court of taking bribes. And although he protested that he had “clean hands and a clean heart,” he was unable to disprove the charges. He was removed from the chancellorship, ordered to pay a fine, and briefly imprisoned in the Tower of London; although James I ultimately rescinded his fine and pardoned him, the wind had been thoroughly taken out of his sails. He died five years later of pneumonia, without coming close to finishing his Great Instauration.7

  8.1 THE NOVUM ORGANUM

  But the Novum organum continued to shape the seventeenth-century practice of science. In 1662, King Charles II granted a royal charter to the Royal Society of London for Improving Natural Knowledge, a gathering of natural philosophers who were committed to the experimental method of science; they were all students of the Novum organum, devotees of the Baconian methods. The poet Abraham Cowley, himself an enthusiastic amateur scientist, wrote the Royal Society’s dedicatory epistle; it was all in praise of Francis Bacon, who had overthrown ancient authority with “true reason”:

  Authority, which did a body boast,

  Though ’twas but air condens’d, and stalk’d about,

  Like some old giant’s more gigantic ghost,

  To terrify the learned rout

  With the plain magic of true reason’s light,

  He chas’d out of our sight,

  Nor suffer’d living men to be misled

  By the vain shadows of the dead.

  The experimental method finally allowed man to look directly at nature, rather than wrestling with logic:

  From words, which are but pictures of the thought,

  Though we our thoughts from them perversely drew

  To things, the mind’s right object, he it brought . . .

  Who to the life an exact piece would make,

  Must not from other’s work a copy take . . .

  No, he before his sight must place

  The natural and living face;

  The real object must command

  Each judgment of his eye, and motion of his hand.8

  The lines are, self-consciously, modeled on Lucretius’s praise of Epicurus. Just as Epicurus had broken the bonds of superstition with his atomism, so Bacon broke the bonds of Aristotle with the experimental method.

  “Bacon’s grand distinction,” observed Macvey Napier in a classic 1818 speech, “lies in this, that he was the first who clearly and fully pointed out the rules and safeguards of right reasoning in physical inquiries.” Finally, a method was in place that would allow natural philosophers to “look with both eyes,” as Copernicus had asked, and come to conclusions based on their observations.9

  To read relevant excerpts from the Novum organum, visit http://susanwisebauer.com/story-of-science.

  FRANCIS BACON

  Novum organum

  (1620)

  Book I begins with “Aphorisms,” brief independent statements that lay out Bacon’s objections to the current methods in use in natural science; Book II develops his alternative proposal.

  The nineteenth-century translation by James Spedding and Robert Ellis is still the most commonly reprinted. It can be read in multiple free e-book versions, such as

  The Philosophical Works of Francis Bacon, trans. and ed. James Spedding and Robert Ellis, vol. 4, Longman (e-book, 1861, no ISBN).

  A more recent translation with introduction, outline, and explanatory notes is

  Francis Bacon, The New Organon, ed. Lisa Jardine and Michael Silverthorn, Cambridge University Press (paperback and e-book, 2000, ISBN 978-0521564830).

  The notes are useful, but the translation, while more contemporary, is not always clearer. For example, the Spedding and Ellis translation of Aphorism XII in Book I reads:

  The logic now in use serves rather to fix and give stability to the errors which have their foundation in commonly received notions than to help the search after truth. So it does more harm than good.

  Compare the Jardine and Silverthorn translation:

  Current logic is good for establishing and fixing errors (which are themselves based on common notions) rather than for inquiring into truth; hence it is not useful, it is positively harmful.

  NINE

  Demonstration

  The refutation of one of the greatest ancient authorities through observation and experimentation

  Therefore it will be profitable . . . by the frequent dissection

  of living things, and by much ocular testimony, to discern

  and search the truth.

  —William Harvey, De motu cordis, 1628

  Francis Bacon, still untarred by scandal, was at the height of his political career when William Harvey carried out his first public dissections in London.

  Harvey was thirty-seven years old, short, energetic, a machine-gun lecturer who mixed English and Latin as he explained the structure of the corpse in front of him, pointing out the internal organs with the “fine white rods” provided for him by the Royal College of Surgeons. He had just been appointed Lumleian Lecturer in Anatomy, a post that required him to teach a twice-weekly class on the human body and, during the winter (when the corpse would putrefy more slowly), to supplement his lectures with the dissection of an executed felon.1

  He was expected to base his work on the classic anatomy texts of Galen, the second-century physician who had supplemented his traditional Hippocratic education with years of animal dissection. Galen had argued that an understanding of the body could come only through knowledge of its structures; his numerous writings and anatomical studies, reintroduced to European physicians by twelfth-century translators, had become the foundation of all contempora
ry medical knowledge.

  But Galen, a Greek-speaking citizen of the Roman Empire, had inherited a double taboo against human dissection. The ancient Greek belief that proper burial was necessary before the soul could enter the Elysian Fields had given way to the Roman superstition that the unburied roamed the earth in misery; and even those rationalists who believed in neither the soul nor the afterlife generally accepted that human bodies should be decently interred, not cut apart. Aside from a small pocket of rogue anatomists in Alexandria (Herophilus and Erasistratus, working in the third century BC), Greek and Roman medical men studied dogs, cats, bulls, and occasionally apes, extrapolating their discoveries to the still-mysterious human body.2

  With the resurrection of the Galenic tradition came a growing impulse to check Galen’s findings against actual human anatomy; and the Christian West was, on the whole, less superstitious about the body than the ancients had been. Human dissection seems to have been reintroduced into university lectures, slowly and sporadically, beginning around 1315 or so, and the practice gained traction when Pope Sixtus IV declared, in 1482, that there was no theological reason to avoid human dissection as long as the remains were given Christian burial afterward.3

  In Harvey’s day, medical training at Italian universities was the most likely to make use of human subjects for anatomy; Jacopo Berengario da Carpi, a lecturer at Bologna, was said to have dissected “several hundred” human bodies, and his illustrated guide to the human body is one of the earliest works of anatomy to contain accurate drawings of the structure of the heart, appendix, and uterus. And it was a professor at the University of Padua, Andreas Vesalius, who had mounted the most serious challenge yet to Galen’s authority: De humani corporis fabrica, a massive manual of anatomy, illustrated with scores and scores of detailed drawings done from actual dissections. Accurate anatomical knowledge, argued Vesalius, had to be the foundation of all medical learning and practice, and anatomists had to look with their own eyes; they should never simply rely on the teachings of past authorities, as was too often done in university training. “As things are now taught in the schools,” he complained, “with days wasted on ridiculous questions, there is very little offered . . . that could not better be taught by a butcher in his shop.”4

  The Fabrica, published in 1543, established a particularly strong practice of hands-on anatomy at Padua; and William Harvey had chosen to travel to Padua for his medical degree. There he was taught in the tradition of Vesalius, who exhorted his students to work hard at “dissecting and examining in person the fabric of the human body, and then carefully comparing it with the teachings of Galen.”5 This close observation—the “looking with both eyes” that Copernicus had recommended, in frustration—had revealed to Vesalius plenty of places where Galen’s conclusions were obviously, demonstrably, clearly wrong.

  Yet even half a century after the Fabrica, Harvey was expected to base his lectures on Galen, the “father of medicine”; those texts were treated with as much respect and deference as Aristotle’s Physics and Ptolemy’s Almagest.

  •

  In his very first year as Lumleian Lecturer, Harvey flat-out contradicted the master.

  “It is shown by the application of a ligature,” his lecture notes read, “that the passage of the blood is from the arteries into the veins. Whence it follows that the movement of the blood is constantly in a circle, and is brought about by the beat of the heart.”6

  This was not at all what Galen had taught.

  Galen’s own observations, mostly of animal anatomy, had revealed that the heart had two chambers, and that the blood in the right chamber was darker than the blood in the left. But dissection couldn’t reveal exactly how these chambers worked. So Galen theorized that each chamber pumped a different kind of blood.

  The darker blood in the right-hand chamber, he believed, was actually manufactured by the liver. The stomach digested food into a milky nourishing liquid called chyme, which was then sent to the liver, which transformed the chyme into “venous blood” and sent it out through veins (which, Galen explained, all originated in the liver) to nourish the organs of the body. Some of it went into the right chamber of the heart, where it was then sent to feed the lungs.

  Arteries, on the other hand, carried a different sort of blood. Air—pneuma, “vital spirits”—entered the body through the lungs and then traveled from the lungs to the left-hand chamber of the heart, where it was combined with venous blood and transformed into “arterial blood”—thinner, brighter, and quicker than venous blood. Then the arteries carried these vital spirits, by way of the arterial blood, to the organs as well. Food and vital spirits, venous blood and arterial blood—the organs of the body needed both to function.

  But neither kind of blood needed a pump to send it along.

  The organs were thought to attract venous blood to themselves whenever they were in need of food, with a sort of sucking power. Arterial blood was moved along by the pulsating motions of the arteries themselves. The function of the heart was merely to suck in air and venous blood, and transform them into arterial blood.

  So, the pulsing action of the heart (the Greeks could hear a heartbeat as well as anyone else) was explained away as an effect, not a cause. Draw in a breath, and the pneuma rushes into your lungs and then travels from the lungs to the left chamber of the heart; when it comes into contact with the venous blood there, it heats the venous blood to the boiling point. As the heated blood expands, the heart expands to hold it (“diastolic” action, from the Greek diastole, “dilation”). Then the blood cools and rushes out into the arteries; the heart relaxes and contracts back to its original size (“systolic” action, from systellein, “to contract”).

  There was one problem with this scheme; it required venous blood to move somehow from the right-hand chamber of the heart over to the left-hand chamber, so that it could be combined there with pneuma. And there didn’t seem to be any connection between the two chambers.

  So Galen acted against his own observations, allowing (in an Aristotelian sort of way) his overall theory to dictate physical reality. There must be pores, he wrote, too small for the eye to see, between the right and left chambers of the heart; through these pores, venous blood seeped from the right to the left.7

  This was exactly the sort of deductive thinking that Francis Bacon had deplored.

  Harvey had multiple problems with the Galenic theory. First, he could find no observational proof of these infinitesimal pores. Second, so far as he could see, the two chambers of the heart were very much the same in structure; how could this be, if they performed such different functions? Third, arterial blood and venous blood seemed to be exactly the same in every quality except their color, so it seemed unlikely that one contained digested food and the other air. Fourth, the artery that led out of the left chamber of the heart and the vein that led out of the right seemed to have about the same capacity—but according to Galen, the artery carried arterial blood to the entire body, and the vein only carried venous blood to the lungs. Why did the lungs need so much blood?8

  Harvey needed a new theory that was based on his structural observations and that he could arrive at inductively—by examining the heart and its function, and by testing both his theories and Galen’s by experiment. For a decade and half, he worked to elaborate this theory. He measured the amount of blood pumped out by the heart with each beat, and realized that Galen’s theory required more blood than the body could hold. He dissected the hearts of animals and saw that they behaved like muscles, and that the contraction of the heart was the active, working phase of its movement—not a relaxing, as Galen had theorized. He painstakingly dissected veins and arteries in search of the valves that helped blood to flow in one direction—not wash back and forth, as Galen’s model demanded. He also dissected animals that were still alive, a practice revolting to us now but legitimate medical research back then, so that he could watch the heart in action. “No one,” he told a visitor later in his life, “has ever rightly asc
ertained the use or function of a part who has not examined its structure, situation, connections by means of vessels and other accidents in various animals, and carefully weighed and considered all he has seen.” 9

  All of this was Baconian, the new experimental method in practice—although both Francis Bacon and William Harvey would have rejected this idea with scorn. Far from criticizing Aristotle, Harvey held him up as an authority, primarily because Aristotle had believed that the heart was the most important organ in the body (Galen gave this honor to the liver). Harvey had actually treated Bacon for gout during Bacon’s years as lord chancellor, and hadn’t taken to him; he remarked that Bacon wrote philosophy like a politician (an insult), and wrote to a friend that the chancellor’s eyes were “like the eye of a viper.”10

  For his part, Bacon had a low opinion of doctors. An entire section of the Advancement of Learning is devoted to the shortcomings of the field of medicine. In Bacon’s view, doctors as a race were far too lax about rigorously searching out causes and effects, too willing to try superstitious or irrational cures, careless about the makeup of their medicines, and insensitive to their patients’ pain.

  But Harvey kept on with his Baconian experimentations, building up layer after layer of support for his new theory. In 1628 he published his findings in Latin as De motu cordis (“On the Motion of the Heart”); an English translation was in circulation by 1653.

  In De motu cordis, Harvey proposed that blood was pumped from the right side of the heart into the lungs and then moved from the lungs to the left side of the heart, and from there throughout the body by way of the arteries. It then returned to the heart by way of the veins, creating a complete circle. Every part of this system was demonstrable except for one—the pathway by which the blood moved from the arteries back into the veins.