Let's say when we measure the brainwaves of someone who is actually deluded and the brainwaves of someone who is fervently religious, they match up to an extraordinary degree. Are we justified to say that the religious person is deluded base on this observation of matching brainwaves alone? Can we judge the propositional content of a belief as to its truth value by brain activity? Can scientific neurological experiments determine the truth and falsity of propositional content or are arguments the only way to determine the truth and falsity of propositional content? Can we appeal to brainwave activity to invalidate theism? Galen O.

Interesting question(s)! I'm afraid that it will be very difficult to replace arguments and the different "tools" philosophers use with neurological data. First, I assume that in identifying a subject as "deluded" we would have to know the falsehood of her belief and perhaps identify which fallacies she has committed. We would also need to think through ideas of mental causation and the degree to which a person's beliefs may be linked to neurological events (are we going to assume a reductive account of the mental? or are we going to allow that propositions, mental acts such as 'believing' are irreducible to the physical, in particular, brain states and processes?. We also need more than neurology to identify and define what is a 'religion.' You seem particularly interested in theism, but some important religions are non-theistic (most forms of Buddhism), and some theists are not religious (Richard Taylor may have been a good case of this).

Still, there are some common sense ways in which philosophers have regularly assumed that certain physical and mental conditions are more or less conducive to production philosophical reflection. In ancient Greece, when wine was sometimes consumed during philosophical dialogues, they were careful to mix water and wine to insure that the philosophers remained fit for disciplined inquiry. And today, most of us are aware that philosophical acuity is not enhanced by sleep deprivation, starvation, extremely high heart racing, migrain headaches,organ failure, and (among other things) brain injury. But even in the midst of all these conditions, we still have to study the arguments and reasons that are relevant. Imagine a graduate student stumbles into a seminar. He has not slept in five days, he has not eaten in three days, his heart rate is off the charts, his organs are failing, he has a splitting headache and he sustained brain injury from a car crash, and yet he manages to say: "G.E. Moore's refutation of idealism is spurious." Even though we have some reason for thinking the fellow is not fit for clear philosophical reflection, the best thing for us as philosophers would (so long as the fellow is sufficiently stable to talk) be to hear his reasons rather than to rush him out to give him an MRI.

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