## Friday, July 8, 2016

### OF THE PYTHAGOREAN THEOREM, THE HELIOCENTRIC SOLAR SYSTEM, AND PROOF IN THE NONEXISTENCE OF GOD

Anyone reading this essay is probably familiar with the story of the debate between a Christian and an atheist in which the Christian challenges the atheist to prove that God does not exist and then smugly leans back in her chair, knowing that the atheist has to admit that he can’t because “no one can prove a negative.”  But I don’t think this is the proper analysis.  The existence or nonexistence of God is not a question of proof; it is a matter of degree of certainty.

In addressing this issue it’s important to distinguish between deductive and inductive reasoning in the context of the meaning of the term “proof.”  In geometry we were taught the Pythagorean theorem.  (Yes, I know, it’s been a long time since most of us studied geometry.  But, trust me, the square of the hypotenuse of a right triangle is still equal to the sum of the squares of the other two sides.)  This theorem is “proved” using deductive reasoning.  It follows inexorably from the application of the fundamental postulates and rules of Euclidean geometry.

But deductive reasoning is a very different process from the one we use to gain knowledge about the actual nature of the world.  For most of those matters we employ inductive rather than deductive reasoning.

Recall that until several hundred years ago it was accepted wisdom that the sun revolved around the earth.  The sun came up every morning and set every evening.  What could be more obvious?  But when astronomers began observing the sky more carefully, it became evident that a geocentric universe didn’t fit all of their observations.  Instead, a heliocentric model did.  And now virtually everyone believes that the earth revolves around the sun rather than the other way around.

We may feel that we have proved the truth of the heliocentric solar system just as we have proved the truth of the Pythagorean theorem.  But, in fact, the truth values of the two concepts are quite different.  The Pythagorean theorem is absolutely true within the logic system of Euclidean geometry.  However, we can never say that about whether the earth revolves around the sun.  All we can say is that our confidence level regarding the relationship between the earth and the sun is very close to certainty.  This is the same kind of analysis that we have relied upon in establishing the degree of certainty of virtually every other belief that we have entertained about the nature of the world.

Our confidence in the truth of propositions about the world may vary in certainty.  Thus we can each decide our confidence level in the truth of such statements as the following:

• Some individuals have the ability to levitate.
• The universe as we know it began with the Big Bang approximately 13.8 billion years ago.
• Darwinian evolution is responsible for the diversity of life that we observe.
• Humans have free will.

We cannot prove statements regarding the nature of the world through deductive reasoning like we can the Pythagorean theorem.  But through inductive reasoning we can modify our certainty regarding the truth of such statements by making observations that increase or reduce that certainty.

Where am I going with all this?  Well, I believe the same analysis can be applied to statements regarding the existence of a theistic god.  Certainty in belief in a theistic god can be increased or decreased in the same manner as certainty in such beliefs as the existence of free will or Darwinian evolution.

Let’s look at some factors that might affect certainty regarding belief in a theistic god vs. belief in atheism.

1. What if miracles happened frequently rather than rarely or not at all?  I’m not talking here about someone recovering from a seemingly terminal illness or a particular family being spared from a tornado that destroys the homes of scores of other families.

2. What if all the world’s religions were essentially identical in doctrine instead of having widely disparate beliefs, for example, involving one god or three gods or many gods?

3. What if the universe were relatively small and orderly instead of one including over a hundred billion galaxies each having an average of a hundred billion stars?  If humanity is part of a special plan, why would there be the need for such a vast, chaotic universe?

4. What if scripture included specific, accurate scientific information beyond what could have been known by the authors?  The scripture that we have contains virtually no scientifically accurate information.

5. What if human biology were totally different from that of all other species?  Instead, our anatomy, physiology, and microbiological structures are clearly closely related to the remainder of the animal kingdom.

6. What if souls survived death and there was frequent interaction between the souls of those who had died and those still living?  Instead, there is no communication with the dead, no objective evidence of souls surviving death.

7. What if there were no natural disasters that cause suffering?

Of course, none of these factors constitutes “proof” regarding the existence or not of a theistic god.  But we’re not talking about deductive proof here.  We are, instead, talking about inductive evidence that either increases or decreases our certainty regarding our world view.  At some point that degree of certainty rises to the level of reasonable belief.