Nitpick about Plato's Republic

But legality is a matter of collective opinion.

Russell agrees, repeatedly saying that to say something is “unjust” or “unethical” means nothing more than that you do not like it. Of course, if true, that would render pointless all philosophical speculations about justice, ethics or values. Many philosophers have a hard time accepting that. Kant, writing after David Hume took skepticism to its ultimate conclusion, tried to found a system of ethics on strict logic, and Nietzsche in his less-logical way tried to do the same, and even today there are “natural law” theorists (it seems to have something to do with Aristotle, which is a good reason for treating it skeptically).

However – I’m reminded of something else Russell said, in his discussion of St. Anselm’s Ontological Argument (wherein Anselm attempts to prove God’s existence by definition; short version: God is the perfect being, nonexistence would an imperfection):

The same would apply to ethics, wouldn’t it?

True. This comes out, now and then, in SDMB GD threads where it is usually acknowledged that science cannot guide us to the best moral system, because what is “good” can’t be tested scientifically.

On the other hand, we do have a very large consensus on basic morality – murder is bad, theft is usually bad, rape is very bad – and, given that, we can perform scientific tests to see what policies best support that moral “common core.”

We can, thus, compare slave-owning societies to free societies, and see that the latter tend to have more of the overall things we like to call good, and fewer of what we label as bad.

Exactly. Legality, justice, and “good” are all defined by the collective consensus of our society. Some choices are highly polarized and contended: abortion is a key example. But others are so widely agreed-upon as to be nigh-universal, and the abhorrence of slave-owning is high on that list.

Also…I’d be interested in any abstract definition of “justice” that can accommodate extreme class differences among people. Joe gets to live in the mansion and eat pie, but Jack has to pull the plough all day long – on the basis of skin color? I could conceive of “lottery slavery” as not being contradictory to justice: every one of us would, at least, have the same odds as everyone else. But determination by skin color? I can’t see any conceivable way of calling that “justice.”

E.g., from The Republic, Book VI:

I read that and I think of modern political campaign consultants.

Aristotle would have, on the basis that Hellenes, who alone have both intelligence and courage, are naturally superior to, and the natural masters of, the cowardly barbarians of South and the stupid barbarians of the North. I don’t know about Plato.

It has been awhile since I read it but I did not come away with that impression at all. The communal society is structured for interests to match ability, the goal is to maximize innovation. Don’t get me wrong, I had significant issues with the society but then it made me question why I obected to it, which might have been the point all along.

How did it fail?