Rules of Classification
Essential Attributes

We should use essential attributes in classifying things.

An essential attribute is a fundamental one. If we divide a genus according to an essential attribute, we group together things that are fundamentally similar and separate them from things that are fundamentally different.

Because a fundamental attribute underlies and explains many of a thing's superficial attributes, things that are fundamentally similar probably have many attributes in common; things that share a superficial, nonessential attribute may well have nothing else in common.


If we classify animals by color, then animals that have more differences than similarities, such as elephants and mosquitoes, are grouped together, whereas animals that have more similarities than differences, such as cardinals and canaries, are distinguished from each other and placed in different groups.

Consistent Principle | Essential Attributes

Rules of Classification

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