One painter ought never to imitate the manner of any other; because in that case he cannot be called the child of nature, but the grandchild. It is always best to have recourse to nature, which is replete with such abundance of objects, than to the productions of other masters, who learnt everything from her.

A treatise on painting. To which is prefixed a new life of the author, by J.S. Hawkins (ed. 1802)