Do all toposes have a terminal object?

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The terminal object in SET is any one element object. SET is a topos. Do all toposes have a terminal object? What special role do terminal objects play in Topos theory?

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Part of the definition of a topos is having finite limits, and this implies having a terminal object.

Probably the easiest significant thing about terminal objects in a topos is that the subobject classifier $\Omega$ in a topos is the power object of the terminal object, and the classifying arrow of $id_{1}:1\to 1$ is precisely the truth arrow $\top:1\to\Omega$. You can see this in $\mathbf{Set}$ where the subobject classifier is isomorphic to $\mathcal{P}(\{\varnothing\})$.

It is also, when interpreting logical formulas in a topos, the domain of the interpretation of constant terms (i.e. of nullary function symbols) since the terminal object is the empty product.