Why don't we teach children definitions for everyday objects? Wouldn't it help them to have a definition of their mother, or their toy train so that they could recognize them?
It seems not likely. Most kids wouldn't need such definitions. Barring disruptions to family life, children usually recognize their parents or toys. Besides, if they "needed" such definitions, would they need to know, in advance, how to use them? Learning to use definitions is usually what happens during schooling and many schooled people don't learn to do it well, anyway.
But in order to learn to use specific definitions of their parents and toys, would children need to learn how first how to use even prior definitions to recognize the specific ones of their parents and toys? But, then, etc. etc.
How do we avoid this logical regress?
Suppose Harry is someone we all know. It is an everyday kind of question to ask, "Can you describe Harry?" It is somehow odd to ask, "Can you define Harry?" This contrast between what it is not unusual to ask with what it is strange to ask points out an important difference between the activities of describing and defining.
Consider, again, the difference between the following answers to the question "Who is the town coroner?"
1. She's the elderly woman who lives in the green house on Logan Street.
2. He or she is the doctor who is elected to conduct official medical inquiries for the town.
We intuit that describing and defining are, in some ways, similar activities but normally differ in, at least, three dimensions: focus, criteria used, and range. The chart sketched below lays out some differences.
|DESCRIBE||A unique(?) individual|| Easily recognizable, |
|DEFINE|| (A "typical" individual) |
A class (or set)
| (...) Essential |
Sometimes difficult to ...
| Strives for ..., |
free from ...
Scanning the chart, as incomplete as it is, you can see some items which would be problematic for an intelligence, natural or artificial, that relied on only memory and abstraction for categorization, e.g. uniqueness, typicality, context, for a few. (For more on this see Concept as Abstraction)
For a completed chart and an expansion on this essay with practice exercises to explore the relationship between between describing and defining, see https://goo.gl/atrf21 .