The Rational Future Institute

What Is Rationality?

Rationality is something we all value, but which most of us find difficult to clearly define. We tend to think we're rational and others are not. We tend to think that we know what's rational and what isn't. But if we can't precisely define rationality, how can we be sure?

On this page, we'll briefly outline the subject of rational thinking, and provide links to more in-depth material.

The first thing to be aware of is that there is an ideal form of rationality. Humans don't reason in this ideal fashion. Instead, humans are driven to conclusions by intuitions that are rapid, effortless, and mostly unconscious. Our intuitions can approximate rational thinking, but they frequently deviate from the ideal. Our intuitions come with cognitive biases. A cognitive bias is a flaw in our intuition that causes us to reach the wrong conclusion sometimes. Cognitive bias knocks our thinking off of the ideal course, and toward faulty conclusions. Fortunately, it is possible to understand our cognitive biases, and apply a critical thinking process to get us back on course.

The human thinking process

We've compiled a handful of examples of the ways that cognitive bias cause us to make irrational decisions. The books and videos on our resources list also describe studies of cognitive bias.

The principles of rationality tell us how to rationally update our beliefs in light of logic and evidence, and how to practically incorporate these beliefs into our decision-making. This is the imprecise definition of rationality that most thoughtful people can agree on. It tells us what the principles do, but  not what the principles are.

Rational thinking is following the ideal set of rules for inferring conclusions from known facts and new evidence.

No matter what you want to do, no matter what values you want to satisfy, you'll need an accurate picture of your self and the world around you. This is what rationality provides. 

How To Know: The Principles of Rational Inference

The principles that tell us how to update our beliefs are called the principles of rational inference, and these principles are precise technical rules.

The first principle of rational inference is called deduction. Deduction tells us how to infer new specifics from general rules. For example, if all cats are mammals, and Fluffy is a cat, then we can infer that Fluffy is a mammal.

The second principle of rational inference is called induction. Induction is a principle that allows us to infer general rules from specific past experiences. Induction gives us probability estimates or relative probability estimates. For example, the fact that heavy objects always fall to the ground when released is known by induction. If a heavy object floated into the sky when released, there would be no contradiction, but we do rationally believe that such an occurrence would be unlikely. The technical rules of induction tell us how we should update our confidence in a theory based upon our experience.

These principles are exclusive. There are no other ways to rationally infer things, except by methods that can be justified by these principles.

Deduction and induction are the only ways to make rational inferences.

Any deliberate reasoning process which violates these rules is irrational. But before we write off all human thinking as irrational, it's important to understand how humans think, and how they approximate ideal reasoning.

Inference: Ideal versus Human

An ideal thinker would only believe things that were rationally justified by the two principles of rational inference. We humans are not ideal rational thinkers, and, for us, this isn't always a bad thing.

In recent decades, researchers in psychology and behavioral economics have discovered that the human mind thinks in two distinct modes. The first mode of thinking is fast, intuitive, automatic and effortless. Automatic thinking is also subconscious. The second mode of thinking is slow, logical and requires deliberate effort.

Automatic thinking is invaluable for human living. Without our automatic modes of thinking, we would be unable to dance, drive cars, or interact with people in the social fashion to which we are accustomed. Most of the things we do every day are automatic. However, automatic thinking is prone to certain kinds of errors. In order to get quick answers, the human mind takes shortcuts. It sacrifices accuracy to get speed. There are hundreds of examples of ways that automatic thinking leads us to incorrect and irrational answers. Some of these examples are amusing, and others, like stereotyping or self-justification can be quite disturbing. These automatic deviations from ideal rationality are known as cognitive biases.

The logical mode of our thinking usually works to correct our automatic judgments, and make them more rational. The logical side of our thinking is what gives rise to critical thinking.

Critical thinking is a deliberate attempt to correct our cognitive bias, and return to more ideal rational thinking.

Unfortunately, we cannot always muster the effort to engage our logical thinking mode. This happens when we are fatigued, when we are disinterested. On other occasions, we engage our logical faculties, but they don't protect us because we don't know the right way to expose the errors in automatic thinking.

Values: How to Decide

Ideal inference is essentially value-free. When evaluating the facts, values are irrelevant. Valuing a possible answer does not make it more likely to be correct. For example, most of us would value having a billion dollars in our bank accounts, but our desire for money doesn't make it more likely that our bank account inexplicably contains a billion dollars.

The principles of rational inference allow an ideal reasoner to suspend value judgments and get a more accurate picture of the world. They also allow the ideal reasoner to more accurately forecast the outcomes of each potential choice facing the reasoner. But how does an ideal reasoner pick among his or her choices?

The answer will come as a surprise to many people:

The ideal reasoner chooses the action whose outcome best satisfies his or her values.

Unlike the situation with inferences, there are no value-free decisions. Without our values, we would lack any basis for preferring one choice/outcome over another.

Neurologists have discovered that patients with brain injuries that disable their value and emotion centers can make excellent inferences, but are unable to make simple decisions about what to do.

A rational thinker makes value-free inferences, but value-laden choices.

Whatever values you endorse, rational inference and decision-making can help you satisfy your values.

Knowing Better

Specialized knowledge about cognitive bias and critical thinking has been available for decades, but despite the publication of numerous popular books on the topic of bias and critical thinking, this knowledge has not yet taken root in popular consciousness. If so few of us can define rational thinking, then we must admit that we live in a predominantly pre-rational culture.

How can we do better?

The first step is to create a cultural awareness of ideal rational thinking. Ideal rationality creates a frame for understanding cognitive bias and critical thinking.

Cognitive bias is more challenging to comprehend when it takes the form of a sundry list of psychological phenomena. The concept of ideal versus non-ideal rational thinking creates a narrative for understanding the myriad of biases. Cognitive biases are the ways that we humans predictably deviate from ideal rational thinking.

The same framing applies to critical thinking. Critical thinking looks like a dry list of thinking practices, but how can we describe critical thinking in an intuitive way? Here, again, the frame of ideal rational thinking creates an intuitive narrative for thinking about critical thinking. Critical thinking  can be grasped as a set of techniques that we apply to our automatic inferences to bring them closer to ideal rational inferences.

Framing the issues in terms of ideal rational thought also gives us a sense of progress and a direction for cultural development. The notion of ideal rational inference gives us a potential way to measure the rationality of our inferences and decisions. Measurement, in turn, offers us a way to chart the progress of humanity towards a more rational society a society that better satisfies our values of justice and morality.

Finally, the frame gives us a basis for altering our educational institutions. The principles of rational thought and an understanding of our shared cognitive biases are things that every citizen should be exposed to in school.

More Information

Our Rationality FAQ
Why these rules of rationality? See our philosophy page.


Copyright 2011 Rational Future Institute NFP