“A Theory of Justice” by John Rawls is as good a presentation as any on basic moral truisms.
The predominant reason for rejecting Rawls’ conclusion is not the argument, which is good and sound, but rather its consequences.
In the book, Rawls uses a rhetorical device known as the “veil on ignorance.” His aim is to “nullify the effects of specific contingencies which put men at odds and tempt them to exploit social and natural circumstances to their own advantage.” (pg 136 – A Theory of Justice) In short, it is provide circumstances in which we are not hypocrites and honestly apply the standards we apply to other people to ourselves.
At the end of the day, justice and honesty is about applying the same standard to everyone, including ourselves. I’m not saying that this is easy. However, it is blindingly clear that in some instances we don’t even try. For example, if one advocates particularly harsh punishment of an individual to set as a warning for others, that isn’t justice. It is intimidation. It is authoritarianism to enforce fearful obedience. It is the tool of the thug. It has no place in a society that proclaims the only legitimate forms of power is by the consent of the governed.
Another moral truism is that we are only responsible for our own actions and their predictable consequences. Therefore, it is also unjust to punish someone for the crimes of others. However, we should also act on the principles of solidarity. If we notice injustice in the world, if we are doing it, we should stop. If we notice someone else doing it, we should try to stop them. However, when we attempt to stop injustice by other parties, history has shown we must be especially cautious. We must take time to ensure and reflect we are applying the same standard to everyone.
Consequently, our moral reasoning is plagued by a veil of selective ignorance, in which evidence that does not conform to the desired world-view or is otherwise inconvenient is ignored. However, in order to be fair, all the evidence must be judged according to the same standard. In fact, according to Rawls’ theory of justice, that is precisely what justice is: fairness.