Yet there are many people who believe that it does, or at least should.
No Christian state makes it apply to men convicted of crime, or against
killing in war, and yet a considerable minority has always held that
both forms of killing violate the commandment. Neither can it be held to
apply to accidental killings, or killings in self-defense, or in defense
of property or family. Laws, too, provide all grades of punishment for
different kinds of killing, from very light penalties up to death.
Manifestly, then, the commandment must be interpreted, "Thou shalt not
kill when it is wrong to kill," and therefore it furnishes no guide to
conduct. As well say: "Thou shalt do nothing that is wrong." Religious
doctrines do not and clearly cannot be adopted as the criminal code of a
state.

In this uncertainty as to the basis of good and bad conduct, many appeal
to "conscience" as the infallible guide. What is conscience? It
manifestly is not a distinct faculty of the mind, and if it were, would
it be more reliable than the other faculties? It has been often said
that some divine power implanted conscience in every human being. Apart
from the question of whether human beings are different in kind from
other organisms, which will be discussed later, if conscience has been
placed in man by a divine power, why have not all peoples been furnished
with the same guide? There is no doubt that all men of any mentality
have what is called a conscience; that is, a feeling that certain things
are right, and certain other things are wrong. This conscience does not
affect all the actions of life, but probably the ones which to them are
the most important. It varies, however, with the individual. What reason
has the world to believe that conscience is a correct guide to right
and wrong?

The origin of conscience is easily understood. One's conscience is