“Courage is the ladder on which all the other virtues mount. ”

"Water", p. 113; this is often quoted as simply: Without courage, all other virtues are useless. <!-- Confessions of a Barbarian: Selections from the Journals of Edward Abbey, 1951-1989 (1994) p. 207 -->
Source: Desert Solitaire (1968)
Context: Has joy any survival value in the operations of evolution? I suspect that it does; I suspect that the morose and fearful are doomed to quick extinction. Where there is no joy there can be no courage; and without courage all other virtues are useless.

Source: The Courage to Create (1975), Ch. 1 : The Courage to Create, p. 13
Context: Courage is not a virtue of value among other personal values like love or fidelity. It is the foundation that underlies and gives reality to all other virtues and personal values. Without courage our love pales into mere dependency. Without courage our fidelity becomes conformism.

i.e., self-control or moderation.
Source: The First Step (1892), Ch. VIII

Variant: Heaven is not gained by a single bound,
But we build the ladder by which we rise
From the lowly earth to the vaulted skies;
And we mount to its summit round by round.
Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 564.

Attributed

In P. Léonard Hansen, Vita mirabilis, 1664, p. 137 https://archive.org/details/wotb_6743752/page/137/mode/2up?view=theater; quoted in Catechism of the Catholic Church, 1992, § 618 https://www.vatican.va/archive/ENG0015/__P1O.HTM.