A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again.
Alexander Pope, English poet 1688 - 1744
In Greek mythology it was believed that drinking from the Pierian Spring would bring you great knowledge and inspiration. Pope is explaining how if you only learn a little it can “intoxicate” you in such a way that makes you feel as though you know a great deal. However, when “drinking largely” it “sobers” you now that you are wise and have a greater understanding, and also “drinking” it “largely sobers” you so you may never acquire complete wisdom and understanding.