Call an internal poset $(P,\leqslant)$ internally inductive if for any object $X$ and any $C\rightarrowtail X\times P$ which is a chain of $X^*(P)$ in $\mathscr S/X$, the object $U_C\rightarrowtail X\times P$$U_C\rightarrowtail X^*(P)$ of upper bounds of $C$ has support no less than $C$. That is, the image of the composite $U_C\rightarrowtail X\times P\to X$ contains the image of $C\rightarrowtail X\times P\to X$, where $X\times P\to X$ is the projection.
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