I have been involved in and read a few conversations about objective morality lately and, as such conversations often do, they all got fairly convoluted fairly quickly.
The reason this happens, generally, is because the person who opposes objective morality wilfully confuses matters so subjectivity, reciprocity, ethics, empathy, maximizing utility, or minimizing harm can be forced in.
The Christian apologist must not only be unwavering when he or she asserts that some things, lying for example, are always morally wrong, they also must be absolutely unwilling to follow the person they are talking to down an endless philosophical rabbit hole.
If you are an apologist of any sort, this very simple objection and answer may be useful next time you find yourself in such a conversation [emphasis added].
It never fails, when the subject of the morality of lying arises in a discussion, that someone will propose the scenario of lying to Nazis to save Jews. You are hiding innocent Jews in your home. Nazis arrive at your front door, seeking to murder those innocents, and they ask you if you are hiding any Jews in your house.
This hypothetical is not new. Saint Augustine considered the question as to whether it is moral to lie to murderers in order to save innocents. The “lying to Nazis to save Jews” scenario is simply a more recent version of that question. And it does not matter, to the morality of the question, if it is extremist Muslims seeking to murder moderate Muslims, or terrorists seeking to murder school children, or the Khmer Rouge seeking to murder doctors and teachers. The basic scenario is the same: murderers ask you if you are hiding innocents, and you in fact are hiding them. Is it moral to lie in that situation?
The classical answer of moral theology is that of Saint Augustine.
Augustine answered that the act of lying is your own sin, for which you would be culpable, but the act of murder is the sin of the other person, for which you would not be culpable. Each human person is bound by the eternal moral law to avoid sin. And neither is it justifiable for you to commit a lesser sin, so that someone else will not commit a greater sin.
[Saint Augustine, On Lying, n. 13.]