Epistemic vs. Instrumental Rationality

What would an ideal rational thinker do?

We think that, at a minimum, a rational mind would reach conclusions that were justified by the evidence in its possession. In other words, the ideal mind would properly adjust its confidence levels in each of its theories based on its experience. It would be able to roughly quantify its confidence, and quantify its confidence in its confidence. For example, rather than making a definitive diagnosis, an ideally rational medical robot might estimate that a patient has a X% +/- Y% chance of having hypertension.

This kind of rationality is called epistemic rationality. The word “epistemic” means “related to knowledge”, and ideal epistemic rationality means that the mind is working to make its knowledge ideally justified.

What kinds of knowledge are we talking about?

Well, an ideal epistemically rational brain might be trying to accumulate all forms of knowledge, with an emphasis on those kinds of knowledge that enhance its efficiency at obtaining and justifying yet more knowledge. It includes knowledge of the sciences, the humanities, and self-knowledge.

Though humans do not reason ideally, we do spend quite a bit of time reasoning epistemically. We read the news and weather to anticipate future conditions of markets, public safety, cultural trends, etc. We chat with our friends to learn how best we can help them and to find out where our social status is heading. We also learn from the missteps of ourselves and others, and identify likely outcomes of our future actions. Of course, being imperfect reasoners, we rarely formalize or quantify our confidence levels, and we sometimes hold conflicting/inconsistent beliefs.

In a world of spin, misinformation, and disinformation, epistemic rationality is critical for becoming a competent consumer, voter, parent, and patient. When we read stories in the news, we employ whatever epistemic rationality we can muster to determine how much of the story to trust, and how to update our beliefs as a result.

Although we are curious beings, curiosity is but one of our motivations. We want to be well fed, loved, healthy, admired, accomplished, and so on. In addition to building knowledge for curiosity’s sake, we also want to build and apply knowledge to satisfy our other values and objectives. That is, epistemic rationality can be seen as primarily instrumental for the satisfaction of our values and desires. While epistemic rationality is about creating the most accurate map of reality, instrumental rationality is about winning at the game of life.

In principle, the two definitions of rationality could come into conflict. Might there be situations in which we more efficiently satisfy our values when we possess a less accurate map of reality?

For example, if we accurately believed that we have been getting good grades in school while studying only two hours a day, we may spend less time studying than we would if we believed we were barely keeping up. Ultimately, we might get better grades and perform better than our peers if we held less accurate beliefs about our present good performance.

In practice, epistemic and instrumental rationality rarely conflict because instrumental rationality needs assurances that less knowledge really does (and will continue to) improve performance. A more pressing problem is the prioritization of our different values. I know my curiosity gets the better of me, and I probably spend time reading articles about politics that could better be spent on fulfilling my objectives.

Despite its technical nature, I focus on epistemic rationality in most of my writing. Partly, this is because epistemic rationality is more objective, less subject to our subjective values. Additionally, there seems to be something of a crisis in epistemic rationality these days. There is so much misinformation and disinformation online, we are all having more difficulty figuring out what is most likely to be true.

Articles on epistemic rationality are usually concerned with statistical reasoning. Articles on instrumental rationality tend to read like self-help. This may make instrumental rationality sound simple. It isn’t. Most of us do not know exactly what we value, what we want out of life. Moreover, devoting attention to our values tends to alter our values! This means the “right answer” is rarely straightforward. And then there is akrasia, our tendency to act against our own better judgment.


    1. Ryan, thanks so much for the great review of my book!

      You say:
      “I don’t think it will be possible to be fully rational at the same speed as intuition, but at least we must be on the lookout for situations which demand the full use of rational reasoning, so that we can resist processing them expediently with intuition alone.”

      Yes! We need to manage limited reasoning strength in the same way that we manage our lack of memory or attention. We develop technologies and best practices that overcome our human limitations. For example, imagine where aviation would be if we relied on soft skills instead of checklists, training, standards, and automation.



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