Rationality

Rationality is the quality of being guided by reason. It describes how we use evidence to form beliefs and how we use reasons to guide our actions. A person acts rationally if they have a good reason for their behavior. A belief is considered rational if it is supported by strong evidence. This concept can apply to many different things. It can describe a mental process like reasoning or a person who possesses these abilities. It can even apply to mental states like intentions and desires. Some scholars even apply it to non-mental things, such as a rational plan for arranging products in a supermarket.

To understand rationality, we must distinguish it from two other terms. The first is arational. Arational things are outside the domain of rational evaluation. Examples include the weather or how your body digests food. The second term is irrational. Irrationality applies to things that belong in the domain of rational evaluation but fail to meet its standards. This includes beliefs or actions that lack good reasons. There is ongoing debate about whether emotions and desires are rational or arational. Some people use the word irrational more broadly to include arational things.

Scholars use several different frameworks to define how rationality works. One major approach is reason-responsiveness. This view suggests that being rational means responding correctly to reasons. For example, the fact that food is healthy is a reason to eat it. Another approach is coherence-based. This defines rationality as the internal coherence among a person's mental states. This means one should not hold contradictory beliefs. It also means one should intend to do what they believe they should do. Some thinkers also use goal-based accounts. These define rationality in relation to specific goals, such as acquiring truth.

There are also deep debates regarding where the source of rationality lies. Internalists believe that rationality depends only on the person's mind. They might argue that rationality involves responding to reasons that the person actually possesses. For instance, it is rational to carry an umbrella if you have evidence of rain. Externalists contend that external factors are also relevant. They might argue that a person should respond to all available reasons. However, some theorists note that a person can be rational even if they lack access to certain facts. An agent might eat fish that is secretly contaminated with salmonella. Because the agent could not have known this, their choice remains rational.

Rationality is often divided into two main types: theoretical and practical. Theoretical rationality concerns the validity of beliefs. It asks if those beliefs are based on sufficient evidence. Practical rationality pertains to actions, decisions, and intentions. These two types can sometimes conflict. For example, practical rationality might require a person to adopt a belief that is actually irrational. Another important distinction is between ideal and bounded rationality. Ideal rationality demands that agents obey every law of logic perfectly. Bounded rationality recognizes that human minds have limited computational power. This makes perfect logic difficult to achieve in practice.

Many academic disciplines study these concepts to solve problems efficiently. In ethics, experts ask if a person can be rational without being moral. Psychology studies how mental processes implement rationality. It also investigates cognitive biases, which are failures of rational processes. Logic studies the specific laws of correct arguments. These laws are essential for the rationality of beliefs. Decision theory is a highly influential field for practical rationality. It states that a decision is rational if the chosen option has the highest expected utility. Other fields like economics, game theory, and artificial intelligence also rely on these ideas.

Finally, we can look at the scale of rationality. Most academic discussions focus on the rationality of individuals. However, there is also social or collective rationality. This pertains to the beliefs and decisions of entire groups. Whether rationality requires reviewing all beliefs from scratch or trusting existing ones is also a subject of debate. There is even a question of normativity, which asks whether people should always strive to be rational. By understanding these different layers, we can better understand how humans interact with the world and each other.