Definition 4.51.

Let \(\phi^*\colon T \to S\) be a morphism of logoi and suppose that \(\phi^*\) admits a left adjoint \(\phi_{\sharp}\colon S \to T\). We say that \(\phi_{\sharp}\) is \(T\)-indexed if, for every morphism \(p\colon X' \to X\) in \(T\) and every pullback square in \(S\) of the form

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the transposed square

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is a pullback in \(T\).