Interesting question, Mr. Spinoza. I wrote a mini-treatise to a Christian poster on the subject of an objective yet secular form of ethics which I submit for the perusal of any interested individual:
Firstly, we got to get a distinction out of the way.
When I say, 'objective morality' I mean a morality that is consistent and objectively applicable to every individual; a morality that doesn't grant any special privileges to anyone arbitrarily.
What I think you think I mean is an absolute morality, something that's an intrinsic, immutable part of existence. Hence why you ask me for 'evidence.' Of course, no physical evidence for morality exists, any more than it does for logic. You would have to presuppose logic in order to prove that it exists.
So just to be clear, I mean an objective morality, not an absolute one.
Now you say that it is circular because you say I presuppose the objectives of morality. That is, to protect people from the undue harm of others. Whereas you say that another person could just as easily come up with different objectives for morality, and could devise a morality to fit those objectives.
It's entirely true that another person could come along and devise a morality that is entirely different. Just as someone could come along and devise a variant of the scientific method.
But here's the thing. Both morality and scientific inquiry are means to an end, one to manage the interaction of humans (or indeed other animals) in a society/group, and the other to discern what is true and what is not.
Like the scientific method, morality is essential for social beings. Neither of these things do people simply have because they 'prefer' them. Both morality and an effective method of determining what is true are essential for the survival of humanity. Our choosing these things over moral and epistemic nihilism is not a matter of preference.
Consider, you are a philosophical nihlist. However, I'm pretty sure that you have a moral sense. You apply a standard of morality to your own behaviour and to that of others, because you have no choice. Morality is an intrinsic part of a human, as well as some other social animals.
One can be a philosophical nihilist in a theoretical sense, but not in a practical one. It is simply not possible to live in a disordered society, nor is it desirable. Yes, people prefer not to live as nihilists, but that still doesn't mean that preference is the basis for morality.
And so, since morality is fundamentally the means by which we attempt to preserve society and the people in it and given that it is an essential part of the human make-up, we have no choice in a applying it. The need for morality is not a matter of preference. Moral nihilism is not a viable option.
Therefore, given the complete inapplicability of nihilism, and the necessity of morality, it is best to develop a kind of morality that is most consistent with the fundamental principles of morality, as mentioned above.
And here it is. You say, 'but someone could come up with different moral prerogatives. Nothing mandates that any person must adhere to your moral objectives.'
Correct. There is nothing that compels anyone to accept any form of morality. Nor is there anything that compels a person to be philosophically consistent.
But given the necessity of humans exercising moral judgement, and given that morality is the means by which humans attempt to best manage their society and protect the individuals in it, some moral ideas will be more effective at securing the objectives of morality than others.
Here you object to the assumption that morality is about 'protecting individuals in society,' because someone else could come up with different moral prerogatives. Yes, they could.
However, as I stated, morality is essential, just as language and emprical inquiry are. Given the essential nature of morality, and these other things, any moral or like system that founded itself (purely theoretically speaking) on arbitrary or absurd premises or notions would be completely abortive from the outset.
You see, someone could similarly develop a system of empirical inquiry that had poor standards of evidence or the like. But such a system would be completely unable to fulfil the purpose for which it exists in the first place. As a result, no one would or could adopt it as a viable system with any useful practical application. And given that knowing what is true and false is a matter of necessity and survival, such a system could not exist other than in a purely theoretical setting.
It is the same with morality. It is something with practical application, and the very objective of it, just like with empirical inquiry, is to achieve some necessary end in the real world. Systems that fail to produce the desired end are discarded.
And so, while it is theoretically possible to develop a morality based on arbitrary principles, it is not practically possible, and therefore such systems would simply be jettisoned as useless.
Actual morality does not work like that. Morality is to be applied in the real world to protect the individuals in it as that is the universal purpose of morality in the first place, although some systems are better at it than others.
The system that I advocate is simply one which seeks to place all people on the same level and give no one any special, arbitrary privilege.
So again you may say, 'Well, that's just your moral perspective. Someone else may say that certain people have certain exclusive privileges.'
To which I say, but such a morality would rely on invoking premises that don't really have any basis, and which do not conform to the fundamental purpose of morality in the first place. At the same time, a morality that relied on such arbitrary axioms could just as easily be twisted to suit any other individual or group.
The whole result of such a morality would complete moral disorder and chaos, and thus the end for which morality is developed in the first place would not be reachable, necessitating the return to its basic premises.
So, given these problems with arbitrary or contradictory morality, I claim that there is a morality that need not cause such complications, and because it is the morality that conforms most closely to the objective, necessary aims of morality, it is therefore this moralty that should be adopted in place of others.
How to affect this if no-one is compelled to be consistent or objective?
Well, I believe it's partly down to the fundamental desire of humans to be consistent and objective. Of course, people will often suspend such things in the case of cultural, ideological or religious bias, but by and large, people still possess the ability to discern what is consistent and what is not, even if it conflicts with what they would rather believe.
I imagine that you're a reasonable person, so, suppose if I persuaded you that one of your positions was inconsistent or unsupported, would you then continue to adhere to it and consciously regard it as still being valid or true? Most likely not, even if you wanted the proposition to be true.
I think morality works in the same way. People can be and are persuaded by ideas that are more consistent and invoke less problems than their own, even if an obstinate person may persist in believing contradictory things.
I see the argument as something more like this:
Morality is necessary -- protecting individuals within society is the necessary goal of morality -- therefore, moral premises can/should only be applied if they are consistent with this necessary aim of morality
Note also that there is no necessary premise of morality that is to arbitrarily elevate or give special rights to any specific group. That is an interpolated idea that is not universally applicable, as it itself is merely asserted and is not an axiom of morality.
Your 'vantage point' is the necessary goal of morality, which is understood, all be it not entirely consistently, by most human beings.
And the definition of logic isn't a matter of preference, but the degree to which one applies it consistently can be. People often fail to notice non-sequiturs and poor deduction and induction.
You see, someone is likewise perfectly able to develop an inconsistent world-view. That does not mean, however, that a truly consistent and logically sound way of looking at reality doesn't exist. It is the same for morality.
As for the consistency of the nihlist; I doubt it very much. Nihlism itself is a non-position with respect to morality and so there aren't even any moral premises to be inconsistent with each other. As for the nihlist themselves, I find it very hard to believe that there is a human that is even capable of lacking a moral sense of some kind, however ill-developed.
Like I said, a person may be, in the philosophical sense, a nihlist, but the fact that they live in a human society as a rational being precludes them for being a nihlist in any practical and even psychological sense.
You will not find physical evidence to support the existence of morality, any more than you will find the evidence you need to show that logic exists. Some things fall out of the sphere of physical, empirical evidence.
To summarise, morality is a necessary part of a human being, and morality has a necessary goal that is not arbitrarily decided by human beings but which may be said to intrinsic to our understanding of morality. Just as we have an intrinsic understanding of what we have to do to find out what is and is not the case in the physical world. The goals of both of these things are not decided by us, nor are they a matter of simple preference.
And I say, that the morality that I believe in is not absolute. It is contingent upon a social context and other rational moral agents. So, you will not find 'evidence' of it as such as it is not some intrinsic part of the universe.
I think you're saying that it is 'just a matter of preference' is too simplistic. I mean, one can say that it is just a matter of preference whether we choose to breathe or not. It's not really something that we can consciously choose to do or neglect to do. In the cases of both morality and breathing, these are things that are simply intrinsic to our nature, while they might not be necessary in an absolute sense.
It's hardly perfect or complete, but I think it does have some value as a rough overview.