 Given this picture, it is natural to apply ‘natural’ to magnitudes as well as properties. For example one might propose that mass is more natural than density. In a late paper, Lewis  (2009)  talks like this (calling magnitudes ‘properties that come in degrees’), although he leaves it open whether they are identical to properties in our sense. Weatherson  (2006),  taking it for granted that magnitudes are not properties, argues that some magnitudes are perfectly natural, and suggests that there may not be any perfectly natural  properties.[9] 