Then we figured out that the simplest interpretation of QM
implies Many Worlds
Many physicists contend this point. They do not consider this interpretation as 'the simplest'. Things hinge on such contentious points as the physical reality of 'the collapse of the wavefunction'. Again, the major thing the Many World interpretation has going for it is that it easily appeals to our imagination -- even, or especially, to the imagination of non-physicists.
We know that the world is deterministic.
Philosophers disagree. It's even the question whether this issue can possibly be settled by any experimental evidence, because of the way we, and our math, are wired to consider everything in causal chains. The evidence isn't really very compelling if you consider the fundamental problems surrounding the question.
Now we know that non-reductionist or dualistic world views
make little sense
Descartes has been critiqued extensively long before science could say anything about mind-matter interactions, because the main shortcomings of the duality argument do not depend on any experimental facts at all.
Now neuroscience is starting to deliver concrete answers.
On the subject of morality, neuroscience cannot possibly deliver any concrete answers at all. You're engaging in the naturalistic fallacy if you think it does. What is the case in the world is not argument for what should be the case in the world. Neuroscience may explain why people hold certain ethical views. It can never explain what ethical view they should hold. What view is 'acceptable', 'the best', 'right'. The answer to that question cannot be reduced to physical facts about the universe.
Philosophy is about reasoning about topics we don't really
understand.
Then we don't really understand logic and math either, do we? The foundations of logic and math are still part of philosophy after all.
And, well, Hume didn't really understand causality, did he? But fortunately, thanks to modern physics, now we do?
> Many physicists contend this point [ ... ] appeal to imagination.
Not so. The vast majority of quantum physicists now agree Many Worlds has won, including Feynman, Gell-Mann and Hawking. The concept of 'collapse of the wavefunction' is silly and shouldn't even be considered for reasons outlined here: http://lesswrong.com/lw/q8/many_worlds_one_best_guess/
> Determinism; Philosophers disagree.
It's just basic reductionism. There are absolutely no fundamental problems surrounding this.
> On the subject of morality, neuroscience cannot possibly deliver any concrete answers at all.
All moral thought and all moral beliefs up to now have happened inside the human brain. Most moral thought is confused and self-contradictory. If we want to figure out why we are moral the way we are, what our "true" moral beliefs are, and how to build societies that flourish, we have to look inside the brain to see how it all works. Either morality has bearing on the real world and is therefore subject to measurement or it has no bearing on the real world and is therefore irrelevant.
> Then we don't really understand logic and math either, do we? The foundations of logic and math are still part of philosophy after all.
Where the line is drawn between math/philosophy isn't a very interesting question.
> And, well, Hume didn't really understand causality, did he? But fortunately, thanks to modern physics, now we do?
Firstly, [1] disagrees with you. Secondly, there is a difference between accepting MWI above other interpretations and actually believing in multiple parallel universes. A difference between accepting the physical and the metaphysical consequences. Thirdly and crucially, MWI depends on QM. Everyone acknowledges QM is probably not a definite description of the universe and non-locality, non-contextuality or another kind of modification would wreak havoc on MWI. If physicists subscribe to MWI but also acknowledge QM seems incomplete, they are being inconsistent.
Concerning determinism:
You say "it's just basic reductionism". But in fact it presupposes reductionism as a viable strategy to determine 'the truth' about determinism. It isn't [2]. Specifically, the question whether we can even determine whether our fundamental theories are deterministic is still wide open. None of the theories, from classical mechanics to quantum mechanics, is clearly deterministic and it remains a question whether it can even be determined whether they are deterministic.
Concerning morality:
No matter how well you can 'measure' my 'true' ethical views on abortion: no measurement will ever tell you what my ethical view on abortion should be. No collection of measurements will ever tell you what a governments policy on abortion should be. At most you can hope to be able to say: in this particular case we should allow it, because that will be best for everyone: the average happiness, productivity and insert-factor-of-importance will be highest if we allow it. However, that kind of judgment presupposes a certain moral system. You can never determine which factors should be important. At most you can measure which factors people rate as most important on average. But again, you presuppose a certain moral system if you choose to use that measurement to determine what to do. If you feel otherwise, there's a large philosophical nut left for you to crack.
I think you underestimate the complexity of these subjects and that your verdicts are premature.
BTW, you guys keep talking about MWI, while the original article is categorically not about MWI. The author describes a Tegmark Level I Multiverse[1], the most conservative of the multiverse models. MWI is Level III, and the author himself says in a subsequent comment[2]:
What I've presented, above, is the argument for the first
type of Multiverse, which I think is correct, and hence,
which I believe in.
I think that anything beyond that is too speculative to be
believed at this point, at least with any sort of
confidence. At least, by me.
And, well, Hume didn't really understand causality, did he? But fortunately, thanks to modern physics, now we do?