“Men perish but principles live.”

Temenidæ Frag. 734
Context: When good men die their goodness does not perish,
But lives though they are gone. As for the bad,
All that was theirs dies and is buried with them.

The Mulberries (1871)

1940s, Third Inaugural Address (1941)
Context: But it is not enough to achieve these purposes alone. It is not enough to clothe and feed the body of this Nation, and instruct and inform its mind. For there is also the spirit. And of the three, the greatest is the spirit. Without the body and the mind, as all men know, the Nation could not live. But if the spirit of America were killed, even though the Nation's body and mind, constricted in an alien world, lived on, the America we know would have perished.

Source: The Cabinet Council (published 1658), Chapter 25

1960s, A Christmas Sermon (1967)
Variant: We must either learn to live together as brothers or we are all going to perish together as fools.

Pelopidas, sec. 18
Parallel Lives

On censorship, in The Man Who Sold the Moon (1950), p. 188; this may be the origin of a remark which in recent years has sometimes become misattributed to Mark Twain: Censorship is telling a man he can't have a steak just because a baby can't chew it.
Context: How anybody expects a man to stay in business with every two-bit wowser in the country claiming a veto over what we can say and can't say and what we can show and what we can't show — it's enough to make you throw up. The whole principle is wrong; it's like demanding that grown men live on skim milk because the baby can't eat steak.

Book VIII, line 84.
Pharsalia

Four Minute Essays Vol. 5 (1919), The Human Heart