By the way, it is no rebuttal to Hume to say, “Admittedly, scientific laws are not 100 percent true, but at least they are 99.9 percent true. They may not be certain, but they are very likely to be true.” How would you go about verifying this statement? How would you establish the likelihood, for instance, of Newton’s inverse square law? It says that every physical object in the universe attracts every other physical object with a force directly proportional to their masses and inversely proportional to the square of the distance between them. This law cannot be tested except by actually measuring the relationships between all objects in the universe. And as that is impossible, no finite number of tries can generate any conclusion about how probable Newton’s statement is. Ten million tries cannot establish 99.9 percent probability—or even 50 percent probability—because there may be twenty million cases that haven’t been tried where Newton’s law may be found inadequate.
At this point we should pause to consider astronomer Neil deGrasse Tyson’s exasperated outburst. Tyson believes it is simply ridiculous to say that scientific laws are not reliable: “Science’s big- time success rests on the fact that it works.” If science did not accurately describe the world, then airplanes would not fly and people who undergo medical treatments would not be cured. Airplanes do fly and sick people are healed in the hospital, and on that basis science must be taken as true. Better to fly in an airplane constructed by the laws of physics, Tyson scornfully says, than to board one “constructed by the rules of Vedic astrology.”I agree that science works—and you won’t get any argument from me about the limits of Vedic astrology—but it doesn’t follow that scientific laws are known to be true in all cases. Consider this dismaying realization. Newton’s laws were for nearly two centuries regarded as absolutely true. They worked incredibly well. Indeed, no body of general statements had ever been subjected to so much empirical verification. Every machine incorporated its principles, and the entire Industrial Revolution was based on Newtonian physics and Newtonian mechanics. Newton was vindicated millions of times a day, and his theories led to unprecedented material success. Yet Einstein’s theories of relativity contradicted Newton, and despite their incalculable quantity of empirical verification, Newton’s laws were proven in important ways to be wrong or at least inadequate. This does not mean that Einstein’s laws are absolutely true; in the future they too might be shown to be erroneous in certain respects.