- > Efforts to advance knowledge that is based on ill-conceived classifications can prove futile, and even harmful. At best, they might result in wasted time spent arguing over terminology. More seriously, they can misdirect research efforts and funding. And at worst, in cases such as the misclassification of medical conditions, the result can be serious harm, including misdiagnosis, improper treat- ment and even death.
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- > Phenomena can be categorized in many ways on the basis of the properties they share. However, categories are useful only if they make it possible to infer further informa- tion, and only if they do so consistently and over a reasonable time period. To distinguish a general category from a more useful one with inferences, we call the latter a ‘class’. Whereas a category simply reflects a repeat- ing pattern of properties, a class additionally indicates that relationships exist between these properties, even if the mechanisms behind the relationships are unknown.
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- > classifica- tion is a purposeful human activity that reflects observations about relationships among prop- erties of phenomena.
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- > In structuring knowledge, scientists should aim to identify classes rather than categories, and controver- sies over classification should be understood and resolved in that context.
The persistent misattribution of properties two instances that are not actually in the class is actually a kind of “source forgetting” problem. People learn to believe that an instance — erroneously labeled as a member of a given class — has a certain property. Then, later, even though they get evidence that the original classification was incorrect, they continue to associate the instance with that property, because they forget why they originally learned that instance–property association.
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- > Taking a classification perspective on scien-
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- > tific discourse suggests a sequence of questions
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- > to ask when studying a domain of phenomena.
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- > What are the properties of interest of these
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- > phenomena? Are there stable sets of properties
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- > common to these phenomena? Are there stable
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- > relationships in some of these sets? And finally,
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- > and most importantly, what is the evidence or
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- > rationale that these relationships reflect the
