One of the great things about the Dominican Order is its clear mission statement: preaching the Gospel for the salvation of souls. This so inspired me that I was prepared to give up everything I had to enter the Dominicans. Among these things was my interest in mathematical physics – after all, what possible use would a doctorate in operator algebras and conformal field theory be to a Dominican friar? As it turns out, my mathematical physics background has been rather more useful than I had anticipated.
Recently, the well-known populariser of theoretical physics, Professor Brian Cox, said that existence of the human soul has been ruled out by experiments. Now, it can be an uphill struggle preaching the Gospel for the salvation of souls when people don’t even believe they have souls. Clearly there is a lot of work to do.
If we are to have an intelligent conversation with someone like Brian Cox, we need to understand what he is saying, and for this, a background in mathematical physics is very useful. Likewise, he should attempt to understand what the Catholic Church is saying. Otherwise, we’ll just end up talking past each other.
The gist of Brian Cox’s argument is that our bodies are composed of particles such as electrons, protons and neutrons. Contemporary physics explains that there are four fundamental forces that account for the behaviour of these particles. But if there is a soul, then there must be a fifth force that strongly interacts with these particles. However, experimental physics suggests that there is no such force. Therefore, experimental physics suggests that souls don’t exist.
The notion of the soul that Brian Cox is appealing to has a long pedigree. According to the Greek philosopher Epicurus, everything around us is composed of atoms, and for the most part they move on trajectories governed by fixed physical laws. But in order to account for human freedom, Epicurus believed that the atoms that made up human beings could sometimes deviate from the trajectories determined by the laws of physics, and thus there had to be a soul by which these deviations occurred.
However, this Epicurean notion of the soul is not what Catholic theologians typically have in mind. According to St Thomas Aquinas, the soul is the substantial form of a living thing. In other words, the soul of something living is the principle by which it is the kind of thing it is and by which it performs its characteristic activities. In the case of human beings, our souls are said to be rational because our most characteristic activity is rational thought. So according to this definition, if Brian Cox said he didn’t have a rational soul, he would be saying that there is absolutely nothing that differentiates him from things that can’t think. I hope this is not something that Brian Cox would admit to.
But this of course raises the question of whether the rational soul could be accounted for entirely in terms of physical laws. There are good philosophical reasons for thinking that it can’t. For instance, in the case of physical laws, it’s conceivable that they might be violated. Otherwise, physicists wouldn’t go to all the effort of performing experiments to verify their theories. However, in the case of rational thought, it is inconceivable that its laws could be violated. For instance, anyone who thinks that the law 2+2=4 could be violated doesn’t know what addition is. The principles of rational thought therefore can’t be reduced to the principles of physics: rational activity and physical activity are fundamentally different.
It might seem we have reached an impasse: on the one hand, there is no evidence for there being a new force that makes physical particles deviate from their natural course, but on the other hand, it also seems impossible to account for rational thought purely in terms of physics. But progress is possible. Given what Brian Cox says, one might be forgiven for thinking that contemporary physics is just Epicurean physics minus the soul. This is not the case. As Brian Cox well knows, contemporary physics is expressed in the language of quantum field theory, and there is currently no scientific consensus on how this theory should be interpreted. But if one’s interpretation of quantum field theory implies rational souls don’t exist, then this seems like a very good reason for rejecting such an interpretation. Thus, the mission of the Dominican Order is still very much alive: we can reasonably believe that we have souls, and that our souls can be saved through the preaching of the Gospel.
Fr Robert Verrill OP is based at the Dominican Priory in Cambridge
This article first appeared in the November 2021 issue of the Catholic Herald. Subscribe today.
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