“Man is the measure of all things: of things which are, that they are, and of things which are not, that they are not.”

Theonas: Conversations of a Sage (1921). Sheed & Ward, 1933, p. 77.

ibid.

Source: Skinny Legs and All

Source: Disturbing the Peace (1986), Ch. 1 : Growing Up "Outside", p. 13
Context: The most important thing is that man should be the measure of all structures, including economic structures, and not that man be made to measure for those structures. The most important thing is not to lose sight of personal relationships — i. e., the relationships between man and his co-workers, between subordinates and their superiors, between man and his work, between this work and its consequences.

Theology and Mysticism

Speech (30 April 1954)

Source: The Ethics of Freedom (1973 - 1974), p. 251
Context: Man himself is exalted, and paradoxical though it may seem to be, this means the crushing of man. Man's enslavement is the reverse side of the glory, value, and importance that are ascribed to him. The more a society magnifies human greatness, the more one will see men alienated, enslaved, imprisoned, and tortured, in it. Humanism prepares the ground for the anti-human. We do not say that this is an intellectual paradox. All one need do is read history. Men have never been so oppressed as in societies which set man at the pinnacle of values and exalt his greatness or make him the measure of all things. For in such societies freedom is detached from its purpose, which is, we affirm, the glory of God.

Variant: We look not at the things which are what you would call seen, but at the things which are not seen. For the things which are seen are temporal. But the things which are not seen are eternal.
Source: A Wrinkle in Time