 As for the conversion of contingency propositions (neither necessary nor impossible), Kilwardby notes that while the converted propositions of indefinite (utrumlibet) contingency are of the same type of contingency, the conversion of natural contingency propositions (true about most cases) results in contingency propositions when contingency means possibility proper (not impossible). There were extensive discussions of the kinds of contingency based on various philosophical ideas in Kilwardby, Albert the Great and their contemporaries (Knuuttila 2008, 540–541).