This is an incomplete summary of OSE ch5, by Karl Popper, focussed mostly on criticism of the claim that Popper is an excellent moral philosopher
p57-58 we must distinguish between natural and normative laws. natural laws are literally impossible to break, but normative ones can be broken.
p58 denies true/false applies to normative laws
p60 people in primitive societies don't see the difference between natural and normative laws. they don't understand that laws of physics cannot be changed and cultural norms can be changed, and how to figure out which is which. (Elliot: this gets more confusing when we consider technology that increases our power over nature, so that natural laws which were major barriers become less important. in that case the laws of nature didn't really change, just our ability to circumvent or harness them.)
p61 says morality is a human construct
p61 says there are no moral facts or moral regularities in nature
p62 says you can never derive moral knowledge from facts or regularities or laws of nature (I take him to mean by "derive" something he would consider possible to do in science, not something impossible in all fields)
p62 gives example saying if you think people getting diseases is alterable, you can still take any attitude about whether this would be a good or bad change
p62 shoves a lot of morality into a category which he dismisses as unimportant and not worth calling morality. it's any way of life which, as a matter of fact, won't work because of the laws of nature. his example is working more and eating less (impossible beyond a certain point). but other examples of things we can rule out in this way include trying to have communism and prosperity, or trying to have trade protectionism without hurting your citizens, or trying to keep children innocent without harming the growth of knowledge. this category Popper dismisses includes important and controversial moral issues. I don't think that Popper knows that the moral question is "How should I live?" and thus "Should I be a communist?" is a question about how to live, and an important moral question, not just a trivial factual matter.
p63 mentions the impossibly of "logically" deriving decisions from facts. well, you can't logically derive scientific theories from facts either. so who cares?
p63 says "simply impracticable" decisions are "pointless and without significance". he is dismissing much of morality as trivial. his attitude denies that attempting projects that will fail is harmful. it second denies that ruling out bad ways of life has any value to someone who wants to learn about how to live. that's ridiculous; as Popper taught us, in science we think up a bunch of theories then use criticism to rule them out until just one stands. we should do the same in morality, and thus we should treat figuring out what won't work as very important -- it's a fundamental part of the knowledge creation process.
p64 representative quote:
But the norm 'Thou shalt not steal' is not a fact, and can never be inferred from sentences describing facts. This will be seen most clearly when we remember that there are always various and even opposite decisions possible with respect to a certain relevant fact. For instance, in face of the sociological fact that most people adopt the norm 'Thou shalt not steal', it is still possible to decide either to adopt this norm, or to oppose its adoption; it is possible to encourage those who have adopted the norm, or to discourage them, and to persuade them to adopt another norm. To sum up, it is impossible to derive a sentence stating a norm or a decision or, say, a proposal for a policy from a sentence stating a fact; this is only another way of saying that it is impossible to derive norms or decisions or proposals from facts.
This doesn't really say why
, it just asserts these things.
Whatever this may be, it is not excellent moral philosophy. That would tell us about how we should live, rather than engaging in technical analysis about the philosophical limits of various statements.
From the fact that communism cannot work (whether this really is a consequence of the laws of physics is controversial, but assume for a moment that it is true) we can, at least in lay terminology, easily infer that purusing communism would be a mistake -- a poor way of life -- immoral. All communists would abandon communism if they thought, factually, that it would not achieve their goals. Technically one could still take the position that communism is good despite believing it would not achieve any good goals, but that would be ridiculous and easy to criticize, so why does it concern Popper so much? Sounds like borderline relativism.
p65 argues that morality is not "entirely arbitrary". concedes it is partially arbitrary. it's not entirely clear what being partially arbitrary means.
p65 gives 3 "moral demands" of mankind: "for equality, for freedom, and for helping the weak". two thirds of these are bad demands! It's very strange that they appear in a book touted as one of the best attacks on communism ever written. Does everyone but Ayn Rand sympathize with communism?
p67 there are "sociological laws" such as laws of economics
The rest of the chapter mostly talks about Plato.