‘Tis fear that proves souls base-born.

[Degeneres animos timor arguit.]

Virgil (70-19 BC) Roman poet [b. Publius Vergilius Maro; also Vergil]

The Aeneid [Ænē̆is], Book 4, l. 13 (4.13) [Dido] (29-19 BC) [tr. Fairclough (1916)]
    (Source)

Of the bravery shown in Aeneas' tale demonstrating what a great, if not even divine, man he is.

(Source (Latin)). Alternate translations:

Feare shews degenerate minds.
[tr. Ogilby (1649)]

Fear ever argues a degenerate kind.
[tr. Dryden (1697)]

Fear argues a degenerate mind.
[tr. Davidson/Buckley (1854)]

Fear proves a base-born soul.
[tr. Connington (1866)]

Fear shows degenerate souls.
[tr. Cranch (1872)]

Fear proves the vulgar spirit.
[tr. Mackail (1885)]

For fear it is shows base-born souls.
[tr. Morris (1900)]

Fear argues souls degenerate and base.
[tr. Taylor (1907), st. 2, l. 14]

'Tis cowardice
betrays the base-born soul.
[tr. Williams (1910)]

Fear proves a bastard spirit.
[tr. Humphries (1951)]

Mean souls convict themselves by cowardice.
[tr. Day Lewis (1952)]

For in the face of fear
the mean must fall.
[tr. Mandelbaum (1971)]

Tell-tale fear
Betrays inferior souls.
[tr. Fitzgerald (1981), ll. 19-20]

If there is any baseness in a man, it shows as cowardice.
[tr. West (1990)]

Fear reveals the ignoble spirit.
[tr. Kline (2002)]

Fear
Always gives away men of inferior birth.
[tr. Lombardo (2005)]

Fear exposes the lowborn man at once.
[tr. Fagles (2006), l. 16]

Fear shows up lesser men.
[tr. Bartsch (2021)]