(For other posts in this series, see here.)

The roots of religion lie in deep evolutionary history. The book Why we Believe in God(s) by J. Anderson Thomson with Clare Aukofer (2011) marshals the evidence from psychology and neuroscience to argue that the tendency to belief in supernatural agencies by itself has no survival value but that it exists because it is a by-product of qualities that evolved for other purposes and which do have survival value, such as the tendency to detect agency behind natural events.

There is no question that believing in the existence of a god satisfies a need for some people. But in our modern enlightened times, and especially for sophisticated believers, it is embarrassing to say that one believes in a god merely because it fills an emotional vacuum. People feel that they need to justify their beliefs in a way that would pass muster with modern science and so they try to find more acceptable reasons based on logic and reason and empirical evidence.

But as this series has discussed, logic and reason alone cannot establish the existence of an entity. The only case in which a purely logical argument can be used is if the negation of a proposition leads to a logical contradiction, showing that the proposition is true. In the case of the existence of god, this would require one to show that the proposition that there is no god leads to a logical contradiction. This is clearly not the case. Assuming that there is no god does not cause any logical problems whatsoever.

The next question is whether the assumption of the non-existence of god leads to any empirical contradiction. But empirical evidence is manifestly within the realm of science, and so this question is subject to the investigative methods of science. Does assuming that there is no god lead to any contradiction with the observable world? Again the answer is no. Science has proven itself quite capable of making the world intelligible without the need to invoke any supernatural agency. Furthermore, the attempt by religious believers to find some phenomenon that is currently unexplained by science (the origin of life, for example) and attribute it to god fails because it is never the case that a scientist is faced with only two theories in investigating a phenomenon, as was the case with the issue of whether the square root of 2 is a rational number, and hence ruling out one theory by contradiction does not make any of the alternatives true.

The reasoning is simple. In science, the choice is never between theory A and the negation of theory A, as was the case with whether the square root of two is a rational number. Scientific conflicts are always three-cornered fights that involve comparing theories A and B with data. Since the number of potential theories to explain any given phenomenon is infinite, the reductio ad absurdum methods cannot be used because even if one could prove that any one of them was wrong it does not mean that any of the others are right. This was articulated by Pierre Duhem long ago.

Unlike the reduction to absurdity employed by geometers, experimental contradiction does not have the power to transform a physical hypothesis into an indisputable truth; in order to confer this power on it, it would be necessary to enumerate completely the various hypotheses which may cover a determinate group of phenomena; but the physicist is never sure that he has exhausted all the imaginable assumptions. The truth of a physical theory is not decided by heads and tails. (The Aim and Structure of Physical Theory, Pierre Duhem 1906, translated by Philip P. Wiener, 1954, p. 190)

Science is a lot more complicated than mathematics. To have any empirical proposition accepted as true, one must provide sufficient positive evidence in support of it, not merely argue against a competing theory. Those arguing in favor of the existence of god have failed to do that. The failure is quite spectacular given the immense powers attributed to their god. What this series has tried to show is that the verdict of science when it comes to the existence of god is an overwhelming “No!”

Some sophisticated religious apologists try to argue that the question of the existence of god is outside the realm of empirical evidence and thus outside the range of science. This raises the question of what is the use of such a god. A recent television series Curiosity on the Discovery channel had one program that dealt with the question Did God Create the Universe?, arising from Stephen Hawking’s recent assertion that god was not necessary to understand the universe. In a discussion after the program, cosmologist Sean Carroll asked Catholic theologian John Haught how the world would look different if there was no god. This is, of course, the key question. If there is no difference, then god is superfluous. If one can point to a specific difference, then that means that there are empirical implications for god’s existence and thus it is a question that can be investigated by science. Haught’s reply? If there is no god, the universe itself would not exist!

This reply aptly captures the poverty of theology. How does Haught know this? He cannot, of course. It is just another example of theology simply making stuff up to find something for god to do. Theology really is nothing more than the field that manufactures excuses for why we see no evidence for god. As H. L. Mencken said, “A theologian is like a blind man in a dark room searching for a black cat which isn’t there – and finding it!”

In this series on the logic of science, I have said that science is not in the business of proving things to be true or disproving them either. Science is in the business of figuring out what works best in any given situation, using the logical and evidentiary methods that it has found useful. The same reasoning that has led to scientific success is what leads naturally to atheism. As population biologist J. B. S. Haldane said, “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.”

Scientific knowledge is always tentative and subject to change in the light of new evidence and never claims that it has the ultimate truth. Some religious apologists seize on this truism to argue that in the absence of achieving absolute truth, scientific knowledge, like religion, is just another form of faith, on an equal footing with it, and thus that the knowledge obtained from each have equal standing. That this is a false equivalency as can be seen by posing the following question: If you had to roll back all the knowledge gained in the last 500 years in just one specific field, which would you choose: to erase what we have learned from religion/theology or what we have learned from science?

I think the answer is obvious.