Full Idea
The unconditioned necessity of appearances can be called natural necessity.
Gist of Idea
Natural necessity is the unconditioned necessity of appearances
Source
Immanuel Kant (Critique of Pure Reason [1781], B447/A419)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.466
A Reaction
Kant can call it what he likes, but this isn't what we mean by 'natural necessity'. We mean a feature of reality, even if we can only use appearances to infer that feature. As usual, they can't tell their ontology from their epistemology.