1. KNOWLEDGE, EVIDENCE, AND ERRORS IN THINKING
The aim of this tutorial is to help you learn to understand the sources of knowledge used in critical thinking.

2. Good critical thinking skills require a sound knowledge base
Knowledge is information or experience we believe to be true and for which we have justification or evidence.
Understanding how knowledge is acquired, as well as having an awareness of the limits of human understanding, is essential in logical reasoning.
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3. Rationalism and empiricism
Our views of the world are shaped by our understanding of truth and the ultimate sources of knowledge.
Rationalists, like the Greek philosopher Plato, claim that most human knowledge and truth derives from reason.
Empiricists, on the other hand, claim that truth and knowledge are derived through empirical evidence collected by our physical senses.
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Immanuel Kant ( )
Kant, a German philosopher, rejected both rationalism and empiricism.
He argued that our experience of reality is not a matter of reasoning or empirical evidence, but is dependent on the structure of our minds.
This means we do not see reality “as it is,” but rather as our brain interprets it by structuring and processing incoming information.
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Evaluating evidence
Evidence is something that tends to prove or disprove a particular view.
It can come from a variety of sources, and as good critical thinkers we must evaluate all evidence before we employ it in critical analysis.
Learning how to evaluate the credibility and accuracy of evidence is a key skill in critical thinking and logic.
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6. The fallibility of direct experience
As noted previously, our brains organize and interpret, rather than directly record, sensory experience.
As a result, direct sense experience, while widely relied upon, is not infallible. Memories are subject to influence from a range of factors, including time, language, and external suggestion. Also, our brains often create false memories of events, and these false memories can be as compelling and believable as real memories. This phenomenon is known as false memory syndrome.
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7. Hearsay and anecdotal evidence
Two types of evidence are notoriously unreliable and require us to approach their claims with skepticism:
Hearsay evidence is evidence that is heard by one person, then repeated to one or more other persons.
Anecdotal evidence, evidence based on personal testimony, is also unreliable due to problems of inaccurate memory as well as the human tendency toward exaggeration and distortion.
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8. Experts and credibility
Although experts are generally among the most credible information sources, it is always important to examine their credentials before accepting their arguments.
Four factors used to determine expertise:
Education or training from a reputable source
Experience in making judgments in the field
Reputation among peers in the field
Accomplishments in the field, such as publications and/or awards
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Evaluating claims
Our analysis of the evidence for a claim should be accurate, unbiased, and as complete as possible.
One thing we must watch out for when evaluating claims is confirmation bias, the tendency to look only for evidence that confirms our assumptions and to resist evidence that contradicts them.
As critical thinkers, we need to consciously develop strategies that compel us to examine evidence— especially that which confirms our prior views—more skeptically, and to be more open-minded about evidence that contradicts our views.
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10. Research is the key to knowledge
Good critical thinkers spend time researching claims and collecting information before drawing conclusions.
Recommended research resources
Expert interviews
Dictionaries and encyclopedias
Library catalogues and scholarly journals
Government documents and Internet sites
When doing research, take accurate notes, cite your sources, and use quotations to acknowledge sources.
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11. Cognitive and perceptual errors in thinking
Most people underestimate the critical role that cognitive and social factors play in our interpretation of sensory data.
Although emotion has traditionally been blamed for faulty reasoning, studies suggest many of our errors in thinking are neurological in nature.
Most of these errors are either cognitive or perceptual errors.
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Perceptual errors
Our minds are not like recording devices. Instead, our brains construct a picture of reality like an artist does, filtering our perceptions and filling in missing information based in part on our expectations.
These processes result in a number of perceptual error predispositions, including distortion of objects, misperception of random data, memorable events error, probability errors, self-serving biases, and self-fulfilling prophecies.
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13. Social errors and biases
As highly social animals, social norms and cultural expectations exert a strong influence on how we perceive the world. These norms and expectations often act as barriers to critical thinking.
Some examples of social errors include the “one of us / one of them” error, social expectations, stereotyping, group pressure and conformity, and group diffusion of responsibility.
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Conclusions
Although knowledge is a crucial component of effective critical thinking, we must recognize that the sources of knowledge, reason, and experience are subject to distortion.
As critical thinkers, we must be aware of these limitations and conduct research thoroughly, with minds open to both supportive and contradictory evidence as we collect and analyze information.
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