But the mere fact that you hear this or that judgement as the voice of conscience, and that consequently you feel a thing to be right, may be due to the fact that you have never given the matter much thought, and have blindly accepted from your childhood whatever you were told was right.
 
[Dass du aber diess und jenes Urtheil als Sprache des Gewissens hörst, also, dass du Etwas als recht empfindest, kann seine Ursache darin haben, dass du nie über dich nachgedacht hast und blindlings annahmst, was dir als recht von Kindheit an bezeichnet worden ist.]

Friedrich Nietzsche (1844-1900) German philosopher and poet

The Gay Science [Die fröhliche Wissenschaft], Book 4, § 335 (1882) [tr. Hill (2018)]
    (Source)

Also known as La Gaya Scienza, The Joyful Wisdom, or The Joyous Science.

(Source (German)). Alternate translations:

But that you hear this or that judgment as the voice of conscience, consequently, that you feel a thing to be right -- may have its cause in the fact that you have never reflected about yourself, and have blindly accepted from your childhood what has been designated to you as right.
[tr. Common (1911)]

But that you take this or that judgment for the voice of conscience -- in other words, that you feel something to be right -- may be due to the fact that you have never thought much about yourself and simply have accepted blindly that what you had been told ever since your childhood was right.
[tr. Kaufmann (1974)]

But that you hear this or that judgement as the words of conscience, i.e., that you feel something to be right may have its cause in your never having thought much about yourself and in blindly having accepted what has been labeled right since your childhood.
[tr. Nauckhoff (2001)]