Lemma 10.53.3. If R is Artinian then R has only finitely many maximal ideals.
Proof. Suppose that \mathfrak m_ i, i = 1, 2, 3, \ldots are pairwise distinct maximal ideals. Then \mathfrak m_1 \supset \mathfrak m_1\cap \mathfrak m_2 \supset \mathfrak m_1 \cap \mathfrak m_2 \cap \mathfrak m_3 \supset \ldots is an infinite descending sequence (because by the Chinese remainder theorem all the maps R \to \oplus _{i = 1}^ n R/\mathfrak m_ i are surjective). \square
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