Whoa, this is an interesting discussion.
In my view, Morality isn't something dependent on people's views, it's objective. I quite like philosopher Michael Ruse's quote in this regard:
"The man who says that it is morally acceptable to rape little children is just as mistaken as the man who says, 2+2=5." Thinking of morality being analogous to rationality is useful and (I think) accurate, our core moral perceptions are just as strong, if not stronger, than our belief in arithmetic or logical truths.
I have two things to say about ethical relativism.
First, just because people agree on a topic doesn't mean the difference of opinion is valid. There are people who believe the earth is flat or the universe is 6000 years old, or that the existence of other minds is illusory. We don't say relativism/withholding judgment about these things is warranted, rather we simply say those people are wrong. Similarly, Nazis and children-sacrificing communities are wrong when they commit morally reprehensible acts. I don't understand why some posters have cited the diversity of human opinion on morality as a defeater to objective morality, it's no more than a description of reality. People may not agree on the age of the universe, but so what? Does it commit us to say that there opinion is of value?
Second, in many cases, ethical diversity is only superficial. In OP's example about death penalty for example, the two parties don't disagree that justice needs to be served, they just have different perceptions about what might be the right way of going about it. In other words, they agree on moral values, but differ on moral duties. I believe much of the ethical diversity in the world are likewise superficial.
Plumpyfoof:
We will never ever see the day where every human in existence agrees that one thing or another is moral.
Inb4 "But wait Plumps, surely taking the life of another innocent person is immoral"
Well I can think of several scenarios in which it could be seen as perfectly acceptable; when your friend has asked for you specifically to pull the plug on them rather than keep them a vegetable the rest of their life for one.
This hardly commits us to moral relativism. The conundrums you mention can easily be averted by specifying a context to a moral statement, e.g. instead of saying "taking innocent lives is wrong in general" we could say "taking innocent lives is wrong except in contexts X, Y and Z".
Additionally, there are some moral statements that are absolutely indubitable. Consider (sorry for the example) "cutting up babies into little pieces just for fun".
Princess Sandshrew:
Do you mean that there are one set of true morals and we only need to find them?
There are two distinct questions here:
1. Does objective morality exist?
2. How do we know which moral values are objective?
Let's not get them mixed up. Someone can answer in the affirmative for 1 but withhold judgment on 2: she could say "I know objective moral values exist, and I can think of some examples of objective moral values (e.g. recreationally raping children is wrong), but I don't know all instances of objective moral values there is." This is crucial, because just because we may not know all the "true moral values", doesn't at all mean no true moral values exists. This consideration also defeats the repeated appeals to "ethical diversity" against objective morality in this thread.
Kosuke:
Chill, man. I was just stating my side of thinking. Well, i think i kinda exaggerated with that statement, though.. so yeah. sorry for that. but what i'm trying to say is that everyone really have an opinion, but these opinions came up because they understand and know that they could defend what their opinion is. so i'll ask you, could you defend that the sky is magenta? how did you say that earth is flat if it is already proven that it is not? why did you say that the blood of unwed virgins are your God-given property? explain why you think that an intravenous administration of 10 percent solution of potassium cyanide at 20mL/day is beneficial to your health? its not that i'm fighting with you or something, its just that i defended my opinion.
There are quite some truths we accept without "evidence" (
a priori truths). Examples are: laws of logic, truths of mathematics, introspective beliefs, human perception of the external reality in general, memory beliefs, and so on.
David Hume in his
Inquiries Concerning Human Understanding argued that science is a non-rational enterprise, because the premise of science- induction- cannot be substantiated with evidence. His problem was, he didn't acknowledge the existence of a prior beliefs, things we simply know to be true without having evidence to believe them. These are integral parts of human noetic structure.