“Real living is living for others.”

Source: North of Beautiful

Letter to Harold Adam Innis (14 March 1951), published in Letters of Marshall McLuhan (1987), p. 223
1950s

Source: Summer and the City

"Interrupting Your Life: An Ethics for the Coming Storm" (2014)

Variant translationː All actual life is encounter.
Variant: All real life is meeting.
Source: I and Thou (1923)

The History of Freedom in Antiquity (1877)
Context: But it may be urged, on the other side, that Liberty is not the sum or substitute for of all things men ought to live for... to be real it must be circumscribed... advancing civilisation invests the state with increased rights and duties, and imposes increased burdens and constraints on the subject... a highly instructed and intelligent community may perceive the benefit of compulsory obligations which, at a lower stage, would be thought unbearable... liberal progress is not vague or indefinite, but aims at a point where the public is subject to no restrictions but those of which it feels the advantage... a free country may be less capable of doing much for the advancement of religion, the prevention of vice, or the relief of suffering, than one that does not shrink from confronting great emergencies by some sacrifice of individual rights, and some concentration of power... the supreme political object ought to be sometimes postponed to still higher moral objects. My argument involves no collision with these qualifying reflections. We are dealing, not with the effects of freedom, but with its causes.... influences which brought arbitrary government under control, either by the diffusion of power, or to an appeal to an authority which transcends all government, and among these influences the greatest philosophers of Greece have no claim to be reckoned.

Flower in Ch. 37 : leaving bastion, p. 355
The Visitor (2002)