In 1873 he helped establish a collective society of fifteen aspiring artists, becoming the "pivotal" figure in holding the group together and encouraging the other members. Art historian John Rewald called Pissarro the "dean of the Impressionist painters", not only because he was the oldest of the group, but also "by virtue of his wisdom and his balanced, kind, and warmhearted personality". Paul Cézanne said "he was a father for me. A man to consult and a little like the good Lord", and he was also one of Paul Gauguin's masters. Pierre-Auguste Renoir referred to his work as "revolutionary", through his artistic portrayals of the "common man", as Pissarro insisted on painting individuals in natural settings without "artifice or grandeur". Pissarro is the only artist to have shown his work at all eight Paris Impressionist exhibitions, from 1874 to 1886. He "acted as a father figure not only to the Impressionists" but to all four of the major Post-Impressionists, Cézanne, Seurat, Gauguin, and van Gogh.