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 and one argued against it. Subsequent quizzing of the subjects revealed that they were less critical of the essay consistent with their views than with the opposing essay. This result is an unsurprising confirmation of the results of ‘They saw a game’ above.

The surprising aspect of Lord et al.’s [1979] finding was this: reading the two essays tended to reinforce a subject’s initial opinion. Lord et al. [1979] concluded that examining mixed, pro-andcon evidence further polarizes initial beliefs. This conclusion is particularly disturbing to scientists, because we frequently depend on continuing evaluation of partially conflicting evidence.

In analyzing this result, Kuhn et al. [1988] ask the key question: what caused the polarization to increase? Was it the consideration of conflicting viewpoints as hypothesized by Lord et al. [1979] or was it instead the incentive to reconsider their beliefs? Kuhn et al. [1988] suspect the latter, and suggest that similar polarization might have been obtained by asking the subjects to write an essay on capital punishment, rather than showing them conflicting evidence and opinions. I suspect that both interpretations are right, and both experiments would increase the polarization of opinions. Whether one is reading ‘objective’ pro-and-con arguments or is remembering evidence, one perceives a preponderance of confirming evidence.

Perception strengthens opinions, and perception is biased in favor of expectations.

Though the preceding case studies demonstrate that perception is much less objective and much more belief-based than we thought, they allow us to maintain faith in such basic perceptual assumptions as time and causality. Yet the next studies challenge even those assumptions. “Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.” With these stunning initial words, the Russo-German mathematician Hermann Minkowski [1908] began a lecture explaining his concept of space-time, an implication of Albert Einstein’s 1905 concept of special relativity.

Einstein assumed two principles: relativity, which states that no conceivable experiment would be able to detect absolute rest or uniform motion; and that light travels through empty space with a speed c that is the same for all observers, independent of the motion of its source. Faced with two incompatible premises such as universal relative motion yet absolute motion for light, most scientists would abandon one. In contrast, Einstein said that the two principles are “only apparently irreconcilable,” and he instead challenged a basic assumption of all scientists -- that time is universal. He concluded that the simultaneity of separated events is relative. In other words, if two events are simultaneous to one observer, then they are not simultaneous to a second observer at a different location. Clocks in vehicles going at different speeds do not run at the same speed.

Although Einstein later relaxed the assumption of constant light velocity when he subsumed special relativity into general relativity in 1917, our concept of an objective observer’s independence from what is observed was even more shaken. Space and time are, as Minkowski suggested, so interrelated that it is most appropriate to think of a single, four-dimensional, space-time. Indeed, modern physics finds that some atomic processes are more elegant and mathematically simple if we assume that time can flow either forward or backward. Gravity curves space-time, and observation depends on the motion of the observer.

Even if, as Einstein showed, observation depends on the motion of the observer, cannot we achieve objective certainty simply by specifying both? Werner Heisenberg [1927], in examining the