I’ve been re-reading Daniel Kahnman’s wonderful book, Thinking, Fast and Slow and came upon the section in which he discusses the ‘affect heuristic’. The affect heuristic is the notion that people often make decisions based on their feelings or emotions about the topic at hand. It is an example of “substitution”, in which “the answer to an easy question (How do I feel about it?) serves as an answer to a much harder question (What do I think about it?)”. (139)

One of the most famous experiments (by Paul Slovic and colleagues) on the affect heuristic involves surveying subjects’ opinions on various technologies, and asking them to list the risks and benefits associated with each technology. The result was fascinating: they observed a very high negative correlation between the estimates on the level of benefits and the level of risks that they attributed to the technologies. This correlation was even higher when they were under a strict time limit. If they favored a technology, it was given a high rating for benefits and very little accompanying risk. When they disliked a technology, they produced very little benefits and listed a lot of disadvantages. As Kahneman notes, “Because the technologies were lined up neatly from good to bad, no painful tradeoffs needed to be faced.”

Then, subjects were given pamphlets which gave brief arguments in favor of a certain technology. Some pamphlets focused on the benefits, while others focused on the risks. The pamphlets were effective in changing the subjects’ mind, but there was an even more interesting result: subjects who only received evidence relevant to the benefits also revised their beliefs about the risk. The same went for the group which only received evidence regarding the mild nature of the risks, they revised the benefits to be more favorable.

This is an intriguing phenomenon, and it immediately reminded me of discourse about the Holy Spirit’s witness in Christianity. In this video about handling doubt, Dr. William Lane Craig argues that the way he knows Christianity to be true (first and foremost – before any arguments or evidence), is on the witness of the Holy Spirit. He knows this “in his heart”, and it gives him a self-authenticating means of knowing that Christianity is true wholly apart from the evidence.

Of course, this sort of reasoning is troubling for a number of reasons (see the ‘Great Pumpkin Objection’ for one line of objection). However, despite the regular objections to this case for veridical knowledge from the Holy Spirit, this seems to me a clear case of the affect heuristic. Craig is substituting a hard question (Does the evidence support the view that God exists?) with an easy one (How do I feel, in my heart, about the existence of God?).

It’s important to note that this does not seem as simple as wish-fulfillment. Atheist philosopher Thomas Nagel has not been shy about his desire for God’s non-existence. He doesn’t “want the world to be like that”. Whether or not this functions as evidence for his atheism is another matter entirely. But this isn’t what Craig, at least not obviously, is doing here. Craig isn’t saying “I want Christianity to be true, so I will believe despite the historical contingency of available evidence”. Instead, Craig is arguing that this self-authenticating witness (his feelings about whether or not God exists) of the Holy Spirit is prior to the available evidence. He’s substituting the easy question for the hard question.

Knowing what we know about the affect heuristic, it seems positively irrational to adopt this sort of view. If the witness of the Holy Spirit presents itself as a sort of feeling (as indicated by “in my heart/soul”), we have serious grounds for wondering about the capability of rationally evaluating the arguments for and against the proposition that Craig feels so strongly toward. In fact, the affect heuristic is probably aggravated in such an emotionally-powerful question like “Does God exist?”.

A final worry that one might have: what could possibly serve as a defeater for the witness of the Holy Spirit? If the witness of the Holy Spirit imparts a feeling of confidence about the proposition “God exists”, then couldn’t a period of doubt be sufficient reason for abandoning belief? If it cannot, then a positive feeling about God’s existence cannot and should not be taken as evidence of God’s existence (let alone be prior to the evidence!).