Why is it that we today find the so-called proofs of the earth’s motion—the stellar parallax and the Foucault pendulum—so convincing when they could not have been guaranteed to convince Bellarmine? The answer is of course that the required new physics has arrived. We are post-Newtonian, and it is in the Newtonian framework that these fundamental experiments provide persuasive evidence. In fact, the Newtonian achievement was so comprehensive and coherent that the specific proofs were not needed. Thus there was no dancing in the streets after Foucault swung his famous pendulum at 2 a.m. on Wednesday morning, January 8, 1851, nor had there been grand celebrations in 1838 after Bessel had announced the successful measurement of an annual stellar parallax. The Copernican system no longer needed these demonstrations to win universal acceptance. Nor was Bradley’s interpretation of aberration a watershed in belief about a moving earth, which is why his work, which came a century before Bessel’s findings, seems so curiously neglected in the heroic retelling of the Copernican conquest.

Without the new physics, Galileo could scarcely have found a convincing apodictic proof of the earth’s motion. Yet he paved the way for the acceptance of the Copernican idea by changing the very nature of science. He argued for a coherent point of view, with many persuasive pointers, and his Dialogo (the Dialogue on the Two Great World Systems), while not containing much new science, nevertheless made it intellectually respectable to believe in a moving planet Earth. While it would be foolhardy to claim that he changed the nature of science single-handedly, he was surely a principal figure in the process. Today science marches on not so much by proofs as by the persuasive coherency of its picture.

No doubt this is old stuff to epistemologists, whose business it is to probe how we understand things. But today it seems to be forgotten by two widely divergent camps. On the one hand there is, especially in America, a hard minority core of anti-evolutionists, who feel that biologists should furnish apodictic "proofs" of macro-evolution, and until that demonstration is in hand, evolution is a "mere hypothesis" that should not have a place in true science. They fail to understand that evolution offers biologists and paleontologists a coherent framework of understanding that links many, wide-ranging elements, that it is persuasive, and that any critique of evolution will fall on stony ground unless it provides a more satisfactory explanation than evolution already does. Of course, the view of the nature of science that I am proposing is a two-edged sword. There are some informed people who passionately believe that a coherent framework of understanding includes the notion of intelligent design, i.e., that a hit-and-miss pattern of mutations by itself is insufficient to explain the extraordinarily pervasive complexity of the biological world.

Let me give a simple example of this dichotomy. I am grasping an apple, which I am about to drop. How can I understand what is about to happen? I can hold that God, the Sustainer of the universe, is recreating the world every moment, and that in each re-creation the apple will be slightly closer to the floor. Or, I can use Newtonian physics and calculate how long it will take for the apple to reach the floor and its velocity when it smashes onto the carpet. This calculation can be very useful, but it will not explain why the apple went down. As Newton himself said in the General Scholium added at the end of the second edition of his Principia, "This most elegant system of the sun, planets, and comets could not have arisen without the design and dominion of an intelligent and powerful being," and then a few paragraphs later, "I have not yet been able to deduce from phenomena the reason for these properties of gravity, and I do not ‘feign’ hypotheses" [17]. In other words, Newton could accept both views of gravity, as God’s action and as a measurable, predictive phenomenon. But the latter view can guide a spacecraft to Saturn, and the first view cannot. Likewise the stochastic view of evolution may help us understand the seemingly capricious ordering of genes on the human chromosomes, whereas the intelligent design hypothesis, which just might be true, has yet to make any brilliant predictions.

But I stated that two widely divergent camps somehow fail to recognize that we come to our fundamental human understanding not by proofs but by persuasion, by the coherence of the picture we construct of the world and our place in it. The other camp is inhabited by the hard core scientists who have adopted scientism as their world view, those who believe that the world of understanding runs by proofs, and who dare those of us who are theists to prove that an intelligent and powerful being exists, with design and dominion as its brief. I cannot prove the existence of a designing Creator any more than I can solve the problem of evil. I am simply personally persuaded that an intentionally created universe, with one of its likely purposes the emergence of conscious and self-contemplative intelligence, makes sense to me, is satisfyingly coherent, and is persuasive.

I am reminded of the poet Robinson Jeffer’s lines about truth in science [18]:

The mathematicians and physics men
Have their mythology; they work alongside the truth,
Never touching it; their equations are false.
But the things work.

As for me, examining the great change in the world view that took place during the so-called Scientific Revolution gives me a richer understanding of the nature of truth in science: it is an intricate process of observation, interpretation, and persuasion. Ultimately it may not be true, but for now it makes sense.