"He had a scientific law for putting a battle on to canvas, one condition of which was that 'there must not be a level spot which is not trampled with gore.' But Leonardo did no harm; his canon was based on literary rather than artistic interests." Analogies with scientific laws have served art and art criticism a very bad turn of late years. Nothing can be more useful to an artist than knowledge of how the emotions are expressed by the contortion of the features; but nobody in his senses could ever imagine that a rule for the expression of anger was rigid throughout and must never be departed from; every one approaching such a rule with a view to practice instead of criticism must immediately perceive that its only use is to be departed from in various degrees. Leonardo's advice for the painting of a battle-piece is excellent if it is understood in the sense in which it was meant,--"everything is what it is and not another thing," as Bishop Butler put it. Be sure and make your battle a battle indeed. It is time we should realise that what the great artists wrote about art is likely to be as sensible as are the works they created. How absurd it is for some one who can neither carve nor paint, much less create, to imagine he easily grasps the rules of art better than a great master! To such people let us repeat again and again Hamlet's impatient: "Oh, mend it altogether!" IV Now it will easily be seen that the causes which shape an art tradition may often be independent of, and foreign to, the will that creates beautiful objects. Religious superstition or formalism may often hem the artist in, and hamper his will in every direction; though it is not wholly accidental that the Greeks had a religion the spirit of which tended always to defeat the conservatism and bigotry of its priests. So that their formalism, instead of frustrating or warping the growth of their art tradition, merely served as a check that may well seem to have been exactly proportioned to its need; preventing the weakness or rankness of over rapid growth such as detracts from the art of the Renascence, and at the same time causing no vital injury. The spirit of the race deserved and created and was again in turn recreated by its religion. Since it is generally recognised that too much freedom is not good for growing life, I think that almost everybody must at this stage have become aware of how immensely stupid the academical idea of a canon appears besides this idea. How suitable both to life and the desire for perfection the Greek practice was! How theologically dense the unprogressive inflexibility of the academical practitioner! And now let us hear Dürer. But first I will quote from Sir Martin Conway the explanation of what Dürer means by the phrase, "Words of Difference."