We add inflationary and non-inflationary fixed-points to higher-order logics. We show that, for every order, it is sufficient to increase the order of the given logic by one to capture inflationary fixed-points and by two to capture non-inflationary fixed-points. In the two cases, restricting to the existential fragment of the corresponding logic turns out to be enough. This also holds for non-deterministic fixed-points.
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