My Oxford University Press blog post on Why Scientists Should Be Atheists generated an interesting discussion in the comments of my blog post here that linked to it. One issue that was raised was my use of the word ‘should’ and why I was singling out scientists with that imperative. Why should scientists apply the same standards they use in science to everything in life? Of course, no one can be forced to do so and people can (and do) compartmentalize their thinking to enable them to be scientists by day and believers in all manner of supernatural entities by night (so to speak).



But it seems odd for scientists to do so because in general scientists seek consistency across the board as part of their professional practice and that drive has been a major factor in generating scientific advances. For example, if we accept the theory of electromagnetism in some areas, then we think it should apply everywhere, unless there is a very good reason as to why it breaks down somewhere else. Ad hoc theories that are used in just one area are seen as temporary placeholders that will eventually be replaced by a comprehensive theory.

Why would we not apply those same principles in every aspect of our lives? As population geneticist J. B. S. Haldane explained in his 1934 book Fact and Faith:

“My practice as a scientist is atheistic. That is to say, when I set up an experiment I assume that no god, angel or devil is going to interfere with its course; and this assumption has been justified by such success as I have achieved in my professional career. I should therefore be intellectually dishonest if I were not also atheistic in the affairs of the world.”

As part of that scientific practice, it is essential for scientists to have ways of determining the existence and non-existence of entities and they have devised ways of doing so. For example, the entire structure of modern society is based on the existence of just two kinds of electrical charges. Using the logic of science, we do not believe in the existence of a third kind of charge. If that same scientific logic and the same methods and standards are applied to other entities such as vampires, fairies, and yes, gods, then we can rule them out too.

I discuss in greater detail the nature of scientific logic that leads to atheism in my book and gave a brief summary in my comment to the earlier post that I will reproduce here for completeness and for those who missed it.

Scientists frequently have to make decisions of whether any entity exists or not and have arrived at decision rules for doing so. In doing so, the default position is non-existence until such time as those arguing in favor of existence can produce a preponderance of affirmative evidence to support their assertion. Sometimes provisional existence status is granted in the absence of such evidence, provided the entity is necessary as an explanatory concept. But that provisional status can be withdrawn if theories change so that the entity no longer is necessary as an explanatory concept. That is precisely what happened with the aether and phlogiston, their provisional status being withdrawn following the introduction of the theory of relativity and the oxygen theory of combustion respectively. On the other hand, in the case of the neutrino and the Higgs boson, they too were granted provisional existence status for decades because they were seen as necessary explanatory concepts but then a preponderance of affirmative evidence (arrived at after over two decades for neutrinos and five decades for the Higgs) resulted in them being granted actual existence status.

If we think god is an entity and not just an idea, then scientists should apply the same standard for its existence claim that we do for every other existence claim, because that kind of search of consistency is a key aspect of scientific practice. Is there a preponderance of affirmative evidence for the existence of any god? Is it a necessary explanatory concept for anything? The answer is no to both. Ergo, scientists can and should conclude that gods do not exist, just like we have concluded that the aether and phlogiston do not exist. To shy away from that conclusion would be, as Haldane said, intellectually dishonest.