Critical Thinking and the Two Senses of Rationality
Introduction to Critical Thinking and Course Objectives
Stuart Brock, the lecturer and coordinator for Phil 105, Crystal Pinkston, introduces the course as a foundational paper essential for university success. The core subject of the course is critical thinking, which is defined as thinking carefully about the reasons for believing something and the reasons for choosing one course of action over another. In its most concise form, critical thinking is synonymous with rational thinking. This definition encompasses two distinct components: reasoning regarding belief (what to think) and reasoning regarding action (what to do).
The Dual Senses of Rationality: Theoretical and Practical
It is essential to distinguish between the two primary senses of rationality. The first is theoretical reasoning, also known as epistemic reasoning. Individuals are considered rational in this sense to the extent that their beliefs are supported by and proportioned to the available evidence. The primary aim of theoretical rationality is the truth. While constraining beliefs to available evidence does not guarantee truth, it is the most effective long-term strategy for obtaining true beliefs and avoiding false ones.
The second sense is practical rationality, which involves reasoning about what to do. In this sense, an individual is rational to the extent that their actions serve their best interests. Unlike theoretical rationality, the goal of practical rationality is utility rather than truth. It acts as a constraint on actions, focusing on what benefits the agent. Irrationality in the first sense involves believing things unsupported by evidence, such as the proposition that . Irrationality in the second sense involves acting against one's best interest, such as smoking obsessively despite a desire to quit and knowledge of the health risks, which illustrates a weakness of will.
The Convergence and Divergence of Rationality
Although theoretical and practical rationality have different goals, they are interrelated because the act of believing is itself a form of action. Consequently, beliefs are subject to both theoretical and practical norms. These two senses of rationality can diverge, where a belief may be rational in one sense but irrational in the other. Stuart Brock provides a medical hypothetical to illustrate this: imagine a patient with a cancer test result indicating that less than of people with the condition survive beyond twelve months. From an epistemic standpoint, it is rational to believe one will not survive the year. However, if believing in one's survival is the very factor that places individuals in that successful bracket, then it becomes practically rational to disbelieve the statistics in favor of survival.
Aristotle and the Essence of Humanity
Aristotle, a foundational figure in philosophy who moved away from consulting oracles toward empirical and logical reasoning, sought to identify the unique essence of human beings. He rejected the notion that being "alive" was the defining characteristic, as plants and other animals share this trait. He similarly rejected "consciousness" because other animals are also conscious. He concluded that humans are uniquely defined as "rational animals." This Aristotelian thesis—that human beings are defined by their capability to reason—was widely accepted for thousands of years until it was challenged by thinkers in the 20th century.
Modern Challenges to the Thesis of Human Rationality
In the 20th century, philosophers and social scientists began to challenge the assumption of human rationality. Quotes from various figures highlight this shift. Oscar Wilde remarked that man is a rational animal who loses his temper when asked to act on reason. Bertrand Russell noted he had spent his life searching for evidence of human rationality. Stuart Sullivan observed that people generally believe they are rational while perceiving their friends as less so. More seriously, psychologists Daniel Kahneman and Amos Tversky stated that psychological evidence is discouraging for those who view humans as reasonable. Richard Nisbett and Eugene Borgida added that psychological experiments have "bleak implications" for human rationality.
Systematic Irrationality and Statistical Errors
The challenge to Aristotle is not merely that some humans are irrational (an exception Aristotle likely recognized), but that human beings are systematically irrational. Data from Ipsos Mori, a UK market research company, demonstrates how public belief fails to proportion itself to available evidence. In England and Wales, the public estimated the Muslim population at , whereas the actual figure was closer to . In Saudi Arabia, the public estimated that a quarter of the population was obese, when the true figure was closer to three-quarters (). In Japan, respondents estimated that over of the population lived in rural areas, while the actual number was approximately . In each case, although statistics were available, the participants' beliefs were not based on that evidence.
Perceptual vs. Cognitive Illusions
To understand why humans are systematically irrational, it is helpful to look at illusions. An illusion is defined as a conflict between how things seem and what is known to be the case; the "seeming" persists even after the truth is discovered. Perceptual illusions—such as optical, auditory (e.g., Shepard's scales), or sensory (e.g., ice on the spine feeling like a burn)—are relatively easy to uncover because we can use one sensory modality to calibrate another. For instance, a pencil in water looks bent (visual), but feels straight (touch).
Cognitive illusions, however, involve a conflict between intuition and knowledge. Unlike the multiple senses used for perception, humans have only one faculty of intuition. This makes cognitive illusions much harder to detect and correct. These illusions create biases that hinder our ability to form beliefs proportionate to the evidence.
Specific Examples of Optical and Perceptual Illusions
Stuart Brock provides several examples of optical illusions to illustrate the persistence of "seeming." These include red lines that appear bent but are straight, vertical red lines of identical length that appear different, and a matrix of white dots where nonexistent black dots appear to move. He also references a color after-image illusion involving a black dot on a black and white image, a rotating woman who appears to move clockwise or anticlockwise, and the famous "dress" that people perceive as either gold and white or black and blue. Finally, he describes a disconcerting immersive artwork at the Chichu Art Museum on Naoshima Island, Japan, where a neon-lit display creates the illusion of a solid wall that is actually an accessible room.
The Wason Selection Task and Confirmation Bias
The first evidence of cognitive illusions came from Peter Watson in 1966 through the "selection task." Participants are shown four cards showing an "A," "D," "4," and "7." They are asked which cards must be turned over to test the hypothesis: "Whenever a card has an A on one face, then its other face is a 4." While many intuitively pick "A" and "4," the correct answer is "A" and "7." The "4" card is irrelevant because the hypothesis does not state that a "4" must have an "A" on the back (it could have a "D" and the hypothesis would still be true). However, the "7" card must be checked because if it has an "A" on the back, the hypothesis is proven false. This task reveals the "confirmation bias," our tendency to look for evidence that confirms our beliefs rather than evidence that might disconfirm or falsify them.
Questions & Discussion
During the lecture, an unidentified student attempted to name the conspiracy theorist mentioned by Stuart Brock. The student stated, "Off the top… I forgot his name off the top of my head. Sorry." Another student correctly identified the individual as David Ike. Stuart Brock confirmed this, noting that David Ike was a former British football player famous for advocating the theory that powerful world leaders are shape-shifting lizards from outer space. Brock used this as an example of theoretical irrationality, as the belief is based on speculation and patterns in ancient stories rather than empirical evidence.
Administrative Matters and Tutorial Information
The lecture concluded with several administrative notes. The tutors for the course were introduced: Natalia, Rachel, and John. Students must be enrolled in one tutorial, and these sessions are scheduled to begin next week, rather than the first week of the term. If students encounter tutorial clashes, they are directed to email the philosophy program administrator for assistance. Students must include their student ID number in all such correspondence to facilitate the process.