One of the basic things that are emphasized in the training of scientists is the importance of evidence in arriving at conclusions. And while that is definitely true within the world of science, I am more and more convinced that when it comes to changing people’s minds about core beliefs (even within science), the effectiveness of evidence is overrated. This is because whatever evidence that is presented that one thinks challenges someone’s deep conviction, they can almost always come up with an alternative explanation that takes that evidence into account without changing the belief itself. This is because given a finite set of data, there are an infinite number of theories that can explain that data. All that increasing the data set does is bring into play a new infinite set of explanations that can accommodate the cherished belief. (I discuss this in some detail in my book The Great Paradox of Science and will not repeat that detailed argument here.)

So what does make people change their minds? When it comes to scientific theories, evidence does play a role but only partially. What happens is that there comes a time when people find maintaining their original belief requires too much work and intellectual contortions and they abandon it in favor of a new belief that makes more sense to them. And I believe that logic and reason are the factors that ultimately trigger such a change.

When I look back at the evolution of my own core beliefs, one major change was going from believing in God to not believing in the existence of any gods or indeed of anything supernatural. I had known the evidence against the existence of gods (such as the existence of suffering) but they did not sway me. People find it fairly easy to work around it. It was also not the case that I lost my faith due to anger about some personal misfortune or other bad experiences with religion that sometimes causes people to abandon religion. My experiences with the religious beliefs of my family and my interactions with all the clergy in my life were uniformly positive. So my emotional pull was to retain my faith, not leave it, feeling that becoming an atheist would somehow be a betrayal of those whom I valued dearly. But there came a point when I just could not logically reconcile the existence of a supernatural deity who could intervene to change the course of events with the idea that the universe works according to scientific laws. The two views were fundamentally incompatible, forcing me to choose, and it was logic that forced me to abandon faith.

Another major area was with the idea of free will. Like most people, I grew up firmly believing in free will. When I came across evidence that challenged the existence of free will, it was not hard to explain that evidence away. But it was only when I looked closely at the theoretical arguments against it that I became convinced that the idea of free will was incompatible with the idea that the brain, just like everything else, worked according to the laws of science and that it did not allow for the existence of a ‘Ghost in the Machine‘.

This brings me to the question of morality. One of the charges that is made against atheists (and thus atheism) is that they have no basis for morality since they deny the existence of universal moral standards of the kinds set by religions in the religious texts. They are accused of having an ‘anything goes’ philosophy that allows them to do whatever they feel like, whether it is harmful or not.

This has always been a specious argument. Whether people behave well or poorly has little correlation with their religious beliefs, with the exception that people who are driven by religious conviction can be convinced to do the most terrible things when they think they are doing their god’s will. They can become even worse when governments become theocratic and endorse their actions. As Steven Weinberg said, “Without [religion], you’d have good people doing good things and evil people doing evil things. But for good people to do evil things, it takes religion.”

In challenging the argument that morality requires religion, I have found that evidence has little effect. One can point to the fact that atheists do not routinely go around murdering people or otherwise doing evil things. In fact some studies show that non-believers commit crimes at lower rates than others. But this has little effect in persuading people that religion is essential if one is to have a moral core.

So what might be a good theoretical argument?

A good starting point might be the Euthyphro dilemma.

Although it was originally applied to the ancient Greek pantheon, the dilemma has implications for modern monotheistic religions. Gottfried Leibniz asked whether the good and just “is good and just because God wills it or whether God wills it because it is good and just”.

The German philosopher and mathematician Gottfried Leibniz presented this version of the dilemma: “It is generally agreed that whatever God wills is good and just. But there remains the question whether it is good and just because God wills it or whether God wills it because it is good and just; in other words, whether justice and goodness are arbitrary or whether they belong to the necessary and eternal truths about the nature of things.”

As stated, the question doesn’t seem to demand an answer either way, leaving it up to each person to choose. But one can make the question more pointed. For example, religious people point to the biblical commandment “Thou shalt not kill” as a religion-based universal moral standard. But what if you pose to them that if the Bible had said “thou shalt kill” instead, would they think it is acceptable to kill? If they say that they still would not, then their source of morality comes from somewhere other than their religion. If they say that their god would never say that, then they are saying that there is indeed an independent moral standard that their god abides by. Actually, the Bible of full of god giving injunctions that people should be killed (usually by stoning) for a large number of infractions that most people who claim to base their morality on the Bible would not dream of doing. Gays, stubborn and mouthy children, adulterers, women who are not virgins when they are married, blasphemers, those who work on the Sabbath, practice wizardry, worship other gods, and even merely pick up sticks on the Sabbath are all targeted for slaughter. When Bob Dylan sang, ‘Everybody must get stoned’ he was making a pun on the word ‘stoned’ but he was also expressing biblical claims.

And then there are people like the Christian apologist William Lane Craig who is a fervent advocate of what he calls the ‘divine command theory’ that says that if their god does or says something, it must be good and that we cannot question it. But he does not say why he does not follow all the commands if they are all good and instead only picks and chooses certain ones. He cannot because that would reveal that he is using a different standard to make his moral decisions.

Whether a god exists or not is an empirical question for which evidence can be provided either for or against. Evidence that goes counter to one’s beliefs can often be the spur that makes people start questioning their beliefs. But I doubt that evidence is the ultimate deciding factor in people arriving at their decision. I would argue that it is logic that provides the final impetus to change beliefs. Beliefs have to collapse under the weight of their internal logical contradictions before they are abandoned.