The Believing Brain - Michael Shermer [159]
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The Power and Poverty of Pure Empiricism
All intellectual movements swing like pendulums through mental space, oscillating between extremes then settling into an ever more narrow groove of ideational range. So it was for the battle of the books as the extremes of fluctuation between authority and empiricism stabilized over time, and where today we (hopefully) recognize the importance of both data and theory. It was Galileo who first discovered the principle of the pendulum, so it is with some irony that I employ the metaphor here. As important as his empirical discoveries were to overthrowing the authoritative dogma of centuries past, when it came to his observations of the planet Saturn, Galileo succumbed to his own cognitive limitations and imagination.
After observing Saturn—the most distant planet of his day—through his tiny telescope, Galileo wrote to his astronomical colleague Johannes Kepler, “Altissimum planetam tergeminum observavi,” “I have observed that the farthest planet is threefold.” He then explained what he meant: “This is to say that to my very great amazement Saturn was seen to me to be not a single star, but three together, which almost touch each other.” He saw Saturn not as a planet with rings as we see it today in even the tiniest of home telescopes, but as one large sphere surrounded by two smaller spheres, thus accounting for its oblong shape.
Why did Galileo—champion of observation and induction—make this mistake? Having praised empiricism as the sine qua non of science, we must now admit its limitative effects. Galileo’s error is instructive for an understanding of the interplay of data and theory, and when it came to Saturn, Galileo lacked them both. Data: Saturn is twice as far away as Jupiter, thus what few photons of light there were streaming through the cloudy glass in his little tube made resolution of the rings problematic at best. Theory: There was no theory of planetary rings. It is at this intersection of nonexistent theory and nebulous data that the power of belief is at its zenith and the mind fills in the blanks. Like Columbus before him, Galileo went to his grave believing not what his eyes actually saw but what his model of the world told him he was seeing. It was literally a case of I wouldn’t have seen it if I hadn’t believed it.
Galileo could not “see” the rings of Saturn, either directly or theoretically, but he certainly saw something, and herein lies the problem. Altissimum planetam tergeminum observavi. As the late Harvard evolutionary theorist and historian of science Stephen Jay Gould noted in his insightful commentary on the Galileo Saturn affair: “He does not advocate his solution by stating ‘I conjecture,’ ‘I hypothesize,’ ‘I infer,’ or ‘It seems to me that the best interpretation.…’ Instead, he boldly writes ‘observavi’—I have observed. No other word could capture, with such terseness and accuracy, the major change in concept and procedure (not to mention ethical valuation) that marked the transition to what we call ‘modern’ science.”23
Over time Galileo returned to Saturn often, and although he never saw the same thing twice, he stuck steadfastly with his original observation and conclusion. In his 1613 book on sunspots, he wrote: “I have resolved not to put anything around Saturn except what I have already observed and revealed—that is, two small stars which touch it, one to the east and one to the west.” Challenged by a fellow astronomer who suggested that perhaps it was one oblong object rather than three spheres, Galileo boasted of his own superior observational skills of “the shape and distinction of the three stars imperfectly seen. I, who have observed it a thousand times at different periods with an excellent instrument, can assure you that no change whatever is to be seen in it.”
The next time he pointed his