Meditations 12.28

To those who ask, Where hast thou seen the gods, or how dost thou comprehend that they exist and so worshippest them, I answer, in the first place, they may be seen even with the eyes; in the second place, neither have I seen even my own soul, and yet I honor it. Thus then with respect to the gods, from what I constantly experience of their power, from this I comprehend that they exist, and I venerate them.

Marcus Aurelius, Meditations 12.28, translated by George Long

If any ask, Where hast thou seen the Gods or how hast thou satisfied thyself of their existence that thou art so devout a worshipper? I answer: In the first place, they are even visible to the eyes. In the next, I have not seen my own soul either, yet I honour it. So then from the continual proofs of their power I am assured that Gods also exist and I reverence them.

Marcus Aurelius, Meditations 12.28, translated by C. R. Haines