On Liberty by John Stuart Mill Chapter 2 Page 101

that they contain and were meant to contain, only a part of the truth; that many essential elements of the highest morality are among the things which are not provided for, nor intended to be provided for, in the recorded deliverances of the Founder of Christianity, and which have been entirely thrown aside in the system of ethics erected on the basis of those deliverances by the Christian Church.

And this being so, I think it a great error to persist in attempting to find in the Christian doctrine that complete rule for our guidance, which its author intended it to sanction and enforce, but only partially to provide. I believe, too, that this narrow theory is becoming a grave practical evil, detracting greatly from the value of the moral training and instruction, which so many wellmeaning persons are now at length