“Der reizt und wirkt”—­the words necessarily recall a much older parable than the catfish—­the parable of the little leaven inserted in a piece of dough until it leavens the whole lump by its “working,” as cooks and bakers know.  Goethe may have been thinking of that.  Leaven is a sour, almost poisonous kind of stuff, working as though by magic, moving in a mysterious way, causing the solid and impracticable dough to upheave, to rise, expand, bubble, swell, and spout like a volcano.  To all races there has been something devilish, or at least demonic, in the action of leaven.  It is true that in the ancient parable the comparison lay between leaven and the kingdom of heaven.  The kingdom of heaven was like a little leaven that leavens the whole lump, and Goethe says that Mephisto, one of the Princes of Evil, also works like that.  But whether we call the leaven a good or evil thing makes little difference.  The effect of its mysterious powers of movement and upheaval is in the end salutary.  It works upon the lump just as the catfish, that demon of the deep, preserves the lumpish cod from the apathy and degeneration of comfort, and as Mephisto, that demon of the world, acts upon the lethargy of mankind working within him, stimulating, driving to production as a devil may.

“A society needs to have a ferment in it,” said Professor Sumner of Yale, in his published essays.  Sometimes, he said, the ferment takes the form of an enthusiastic delusion or an adventurous folly; sometimes merely of economic opportunity and hope of luxury; in other ages frequently of war.  And, indeed, it was of war that he was writing, though himself a pacific man, and in all respects a thinker of obstinate caution.  A society needs to have a ferment in it—­a leaven, a catfish, a Mephisto, the queer, unpleasant, disturbing touch of the kingdom of heaven.  Take any period of calm and rest in the life of the world or the history of the arts.  Take that period which great historians have agreed to praise as the happiest of human ages—­the age of the Antonines.  How benign and unruffled it was!  What bland and leisurely culture could be enjoyed in exquisite villas beside the Mediterranean, or in flourishing municipalities along the Rhone!  Many a cultivated and comfortable man must have wished that reasonable peace to last for ever.  The civilised world was bathed in the element of calm, the element of gentle acquiescence.  All looked so quiet, so imperturbable; and yet all the time the little catfish of Christianity (or the little leaven, if you will) was at its work, irritating, disturbing, stimulating with salutary energy to upheaval, to rebellion, to the soul’s activity that saves from bland and reasonable despair.  Like a fisherman over-anxious for the peace of the cod in his tank, the philosophic Emperor tried to stamp the catfish down, and hoped to preserve a philosophic quietude by the martyrdom of Christians in those flourishing municipalities on the Rhone.  Of course he failed, as even the most humane and philosophic persecutors usually fail, but had he succeeded, would not the soul of Europe have degenerated into a flabbiness, lethargy, and desperate peace?