Mediocrity, or the holding a middle course, has been highly extolled in morality, but little in matters of science, though no less useful and proper here; whilst in politics it is held suspected, and ought to be employed with judgment. The ancients described mediocrity in manners by the course prescribed to Icarus; and in matters of the understanding by the steering betwixt Scylla and Charybdis, on account of the great difficulty and danger in passing those straits.
Icarus, being to fly across the sea, was ordered by his father neither to soar too high nor fly too low, for, as his wings were fastened together with wax, there was danger of its melting by the sun's heat in too high a flight, and of its becoming less tenacious by the moisture if he kept too near the vapour of the sea. But he, with a juvenile confidence, soared aloft, and fell down headlong.
The fable is vulgar, and easily interpreted; for the path of virtue lies straight between excess on the one side, and defect on the other. And no wonder that excess should prove the bane of Icarus, exulting in juvenile strength and vigour; for excess is the natural vice of youth, as defect is that of old age; and if a man must perish by either, Icarus chose the better of the two; for all defects are justly esteemed more depraved than excesses. There is some magnanimity in excess, that, like a bird, claims kindred with the heavens; but defect is a reptile, that basely crawls upon the earth. It was excellently said by Heraclitus, A dry light makes the best soul for if the soul contracts moisture from the earth, it perfectly degenerates and sinks. On the other hand, moderation must be observed, to prevent this fine light from burning, by its too great subtilty and dryness. But these observations are common.
In matters of the understanding, it requires great skill and a particular felicity to steer clear of Scylla and Charybdis. If the ship strikes upon Scylla, it is dashed in pieces against the rocks; if upon Charybdis, it is swallowed outright. This allegory is pregnant with matter; but we shall only observe the force of it lies here, that a mean be observed in every doctrine and science, and in the rules and axioms thereof, between the rocks of distinctions and the whirlpools of universalities; for these two are the bane and shipwreck of fine geniuses and arts.