index 1c2a07b..f7ed3ab 100644
@@ -16,7 +16,7 @@ a set is a collection of things. that's it. but from this absurdly simple starti
**complement** (Aᶜ): everything not in A. the opposite. "people who don't like pizza."
-these four operations let you manipulate categories with precision. every database query (SQL's WHERE, JOIN, UNION, EXCEPT) is set operations on rows. every search engine query (AND, OR, NOT) is set operations on documents.
+these four operations let you manipulate categories with precision. every database query (SQL's WHERE, JOIN, UNION, EXCEPT) is set operations on rows — a fact that makes [[stem/computer-science|computer science]] fundamentally dependent on set-theoretic thinking. every search engine query (AND, OR, NOT) is set operations on documents.
## MECE: mutually exclusive, collectively exhaustive
@@ -77,4 +77,6 @@ this is why definitions matter. not pedantically, but fundamentally. sloppy defi
## the deep point
-set theory is the mathematics of classification. in a world drowning in information, the ability to categorize precisely — to define boundaries, check for completeness, identify overlaps, and reason about relationships between categories — is one of the most practical mathematical skills there is. you don't need to know the axiom of choice to benefit from thinking in sets.
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+set theory is the mathematics of classification. the impulse to classify connects to [[immediate/ordering-and-comparison|ordering and comparison]] — you can't sort things into sets without first deciding what makes them similar or different. taken further, the study of how sets relate to each other through notions of "nearness" and continuity leads to [[structural/topology-as-thinking|topology]], which generalizes set theory into the study of shape and space.
+
+in a world drowning in information, the ability to categorize precisely — to define boundaries, check for completeness, identify overlaps, and reason about relationships between categories — is one of the most practical mathematical skills there is. this kind of precise categorical reasoning is itself a form of [[structural/abstraction-as-power|abstraction]]: stripping away particulars to focus on structure. you don't need to know the axiom of choice to benefit from thinking in sets.
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