A passage from Epictetus
Epictetus, Discourses III.24
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The universe is one, and God, who pervades all things, is one, and substance is one, and law is one, that is, the common reason of all intelligent animals, and truth is one.
Related passages
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Your present opinion founded on understanding, your present conduct directed to social good, your present disposition contented with everything that happens — that is enough.
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Of human life the time is a point, the substance flowing, the perception dull... The only thing that escorts a man on his way is philosophy.
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He who acts unjustly acts impiously. For since the universal nature has made rational animals for the sake of one another, he who acts contrary to nature commits impiety against the highest divinity.