The thrust of Leonardo da Vinci 's argument is that painters who work from nature will produce good work; painters who imitate each other will not. So Giotto was a great painter because he did not merely imitate the works of his master, Cimabue, but being born in the mountains he was guided by nature in his drawing of the animals which surrounded him. Art then declined again, according to Leonardo because painters imitated each other until Masaccio showed by 'his perfect works how those who take for their standard anyone but nature - the mistress of all masters - weary themselves in vain' ( Richter, The Literary Works of Leonardo da Vinci, paragraph 660).
Reynolds accepts Masaccio 's importance but is concerned to stress the need for painters to learn from, and indeed imitate, each other (see Reynolds on Masaccio).