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Fallacious Reasoning About Reality Leads to Bad Theories

A Personal Perspective: Commonly committed but flawed patterns of reasoning.

Key points

  • Reality is independent of human minds, perceptions, mathematics, and social interactions.
  • Four fallacious patterns of reasoning support idealism, empiricism, Pythagoreanism, and social constructionism.

In an era of “post-truth” and “truthiness,” it can be hard to defend the common-sense belief that reality exists independently of how people think about it. Skepticism about reality comes in many flavors, but some of them are based on commonly committed but flawed patterns of reasoning. Here are four reality fallacies that have true premises but reach false conclusions. Each fallacy leads to a bad philosophy of reality: Idealism, empiricism, Pythagoreanism, or social constructionism.

Mental Fallacy (Idealism)

Premise: Mental operations are used in acquiring knowledge of reality.

Conclusion: Reality is mental.

Flaw: Minds do not construct reality, but rather construct representations of reality that may be true or false. The universe has been around for around 13.7 billion years, but human minds have only been around for a few million years. The universe is not a mental construction.

Perceptual Fallacy (Empiricism)

Premise: Perception is crucial for collecting evidence concerning reality.

Conclusion: Reality is perceptual.

Flaw: Evidence depends on perception, but reasoning allows us to go beyond perception to gain knowledge that goes beyond perception, for example about atoms, molecules, forces, quantum wave-particles, viruses, and mental states. Minds can construct good models of reality by combining perceptual experiences with sound reasoning.

Mathematical Fallacy (Pythagoreanism)

Premise: Mathematics is of great value for achieving knowledge.

Conclusions: Reality is mathematical.

Flaw: Mathematics is an invention of humans that is less than 10,000 years old; its value as a scientific tool does not make reality merely mathematical. Science has been very effective by combining mathematical theories with perceptual experiences and deep causal explanations.

Social Fallacy (Social Constructionism)

Premise: The development of knowledge depends on the social interactions of people.

Conclusion: Reality is socially constructed.

Flaw: Social interactions alone are not sufficient to establish consensus about reality which depends on interactions with the world using perception, instruments, systematic observations, and controlled experiments.

All of these fallacies correctly note that human knowledge develops by using perception, other mental operations such as hypothesis formation, mathematical reasoning, and social interactions. But they overgeneralize the importance of single contributions to knowledge while failing to recognize how robustly reality resists human arbitrariness.

Good reasons to believe that reality is independent of human activity include:

1. The universe existed for billions of years before humans came along with our perceiving, thinking, mathematics, and social networks.

2. No amount of thinking, mathematics, and social networks are sufficient to give humans the kind of reality we might want, for example, one free of disease, death, and economic failures.

3. Technology often works powerfully through accrued knowledge about real aspects of the world such as electrons and viruses. Some technologies fail because they don’t get the world right.

4. Even the most clever experimenters with the best instruments, brains, mathematical techniques, and social teams often fail to get the experimental results they want.

Reality is often resistant to human investigation, which should motivate humans toward using perceptions, theories, and experiments to improve our understanding of how the world works. Truth is correspondence to reality, not just what works or what people want to believe.


For further discussion of how science and philosophy work together to gain knowledge of the world, see my book Natural Philosophy.

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