Is the following Wikipedia statement true?
As @Huisman points out, this statement applies only to linear ideal elements. Specifically, the statement does not apply to non-linear elements or, in general, to real elements. The structure of the article suggests this distinction but the single sentence, taken out of context, can be a bit misleading.

Having made that qualification, I think the statement is correct. The only way to prove that it is not correct is to produce a counter example and I can't think of one.