Dear Boy:  Every excellency, and every virtue, has its kindred vice or weakness; and if carried beyond certain bounds, sinks into one or the other.  Generosity often runs into profusion, economy into avarice, courage into rashness, caution into timidity, and so on:—­insomuch that, I believe, there is more judgment required, for the proper conduct of our virtues, than for avoiding their opposite vices.  Vice, in its true light, is so deformed, that it shocks us at first sight, and would hardly ever seduce us, if it did not, at first, wear the mask of some virtue.  But virtue is, in itself, so beautiful, that it charms us at first sight; engages us more and more upon further acquaintance; and, as with other beauties, we think excess impossible; it is here that judgment is necessary, to moderate and direct the effects of an excellent cause.  I shall apply this reasoning, at present, not to any particular virtue, but to an excellency, which, for want of judgment, is often the cause of ridiculous and blamable effects; I mean, great learning; which, if not accompanied with sound judgment, frequently carries us into error, pride, and pedantry.  As, I hope, you will possess that excellency in its utmost extent, and yet without its too common failings, the hints, which my experience can suggest, may probably not be useless to you.

Some learned men, proud of their knowledge, only speak to decide, and give judgment without appeal; the consequence of which is, that mankind, provoked by the insult, and injured by the oppression, revolt; and, in order to shake off the tyranny, even call the lawful authority in question.  The more you know, the modester you should be:  and (by the bye) that modesty is the surest way of gratifying your vanity.  Even where you are sure, seem rather doubtful; represent, but do not pronounce, and, if you would convince others, seem open to conviction yourself.

Others, to show their learning, or often from the prejudices of a school education, where they hear of nothing else, are always talking of the ancients, as something more than men, and of the moderns, as something less.  They are never without a classic or two in their pockets; they stick to the old good sense; they read none of the modern trash; and will show you, plainly, that no improvement has been made, in any one art or science, these last seventeen hundred years.  I would by no means have you disown your acquaintance with the ancients:  but still less would I have you brag of an exclusive intimacy with them.  Speak of the moderns without contempt, and of the ancients without idolatry; judge them all by their merits, but not by their ages; and if you happen to have an Elzevir classic in your pocket neither show it nor mention it.