CatDat

Implication Details

Claim: If a category has disjoint finite coproducts and is regular-subobject-trivial, then it is trivial.

Proof: For any object XX, the unique morphism !:0X! : 0 \to X is a regular monomorphism, as the equalizer of the two coprojections XXXX \rightrightarrows X \sqcup X. Therefore, it is an isomorphism.

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