Forgers understand this principle very well because in trying to present a painting as a 'Renoir' what they do is to carefully maintain as invariant as possible (as resistant to scrutiny as possible) those critical relations ( brushstrokes, texturing etc.) among specified components (colours, oils, aged canvas etc.) which will identify it as that class of production called 'Renoir'. Experts attempt to distinguish fakes" and "the genuine article" by decomposing the artistic unity into its components and relations. The artist's "style" is that peculiar way in which he composed the constituent parts. The way he organised his painting. This Organization must remain invariant for the unity to conserve its class identity.