Pope's rhymes are so neat they can sound smug. Read them as a machine for sounding certain — and notice what the certainty is actually asking you to give up.
Know then thyself, presume not God to scan; The proper study of mankind is man. Plac'd on this isthmus of a middle state, A being darkly wise, and rudely great:
Underlined words and phrases can be tapped for a note
Know yourself, then, and don't try to examine God. The proper subject of study for humans is humans. We are placed on a narrow strip of middle ground: partly wise and partly great, but crudely so.
With too much knowledge for the sceptic side, With too much weakness for the stoic's pride, He hangs between; in doubt to act, or rest; In doubt to deem himself a god, or beast;
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We know too much to be sceptics, and we're too weak to be stoics. We hang in between: unsure whether to act or to rest, unsure whether to think of ourselves as gods or as animals.
That's the whole thing.
Read it again slowly — it gets better the second time.