Evidential: "because I say so"/"because I assert it to be true"/"it is known".
Maybe also "because I am your parent" in some contexts. The claim is true not because the utterer defines it to be so/has the authority or ability to make it so, but instead simply because they claim it to be true. Useful for dealing with annoying children who ask "why" iteratively; not useful for actually convincing anyone of the claim.