Other more or less popular opinions of the way to determine right or wrong are found to be no more satisfactory. Many believe that the question of whether an act is right or wrong is to be settled by a religious doctrine; but the difficulties are still greater in this direction. First of all, this involves a thorough and judicial inquiry into the merits of many, if not all, forms of religion, an investigation which has never been made, and from the nature of things cannot be made. The fact is, that one's religious opinions are settled long before he begins to investigate and quite by other processes than reason. Then, too, all religious precepts rest on interpretation, and even the things that seem the plainest have ever been subject to manifold and sometimes conflicting construction. Few if any religious commands can be, or ever were, implicitly relied on without interpretation. The command, "Thou shalt not kill," seems plain, but does even this furnish an infallible rule of conduct? Of course this commandment could not be meant to forbid killing animals. 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?