Lives of the Cambridge polymath geniuses

Yes, I'd also like to understand better the attraction of communism. Some off-the-cuff ideas:

• It was harder to get good information about the Russian or Chinese communists during certain periods. (No Internet, fewer reliable journalists, less travel in each direction). 
• Non-communist countries were much more violent than post-WW2. There was more homicide and more violence that involved the state (e.g. violence in prisons, colonial violence, civil wars, interstate wars). Maybe the Soviet Union up to 1935 didn't look radically different from non-Communist countries. 
• Economics was less developed and (possibly) fewer smart people had a basic grasp of the field. (Some good arguments against Marxist economics already existed but weren't widely known). 
• The empirical evidence against command economies vs market-based systems was much less clear. (Modern concept of GDP was only developed in 1934!)
• Non-communist countries were very conservative in some ways, e.g. rights for women and ethnic minorities, the special privileges given to the state religion, workers' rights, availability of public education and training. Both the early Soviet Union and Communist China had some policies that were progressive relative to the status quo and to other non-communist countries.
• Communists shouted about and valorized progress, modernization, industrialization, and science. (And the Soviet Union did industrialize pretty quickly and produce fairly impressive science and technology.)   

Incidentally: Russell did visit the Soviet Union and came away with a negative impression. Keynes also visited and had a very negative impression. He was also in a position to evaluate Marx's economics. Here's Keynes' view of Leninism taken from Wikipedia:

How can I accept a doctrine, which sets up as its bible, above and beyond criticism, an obsolete textbook [Marx's Kapital] which I know not only to be scientifically erroneous but without interest or application to the modern world? How can I adopt a creed which, preferring the mud to the fish, exalts the boorish proletariat above the bourgeoisie and the intelligentsia, who with all their faults, are the quality of life and surely carry the seeds of all human achievement? Even if we need a religion, how can we find it in the turbid rubbish of the red bookshop? It is hard for an educated, decent, intelligent son of Western Europe to find his ideals here, unless he has first suffered some strange and horrid process of conversion which has changed all his values.

Jason Crawford's recent post on 19th-century philosophy of progress [LW · GW] seems relevant. Some quotes from it:

• deep belief in the power of human reason
• had forecast progress in morality and society just as much as in science, technology and industry
• progress was inevitable
• the conviction that “the Idea or the Dialectic or Natural Law, functioning through the conscious purposes or the unconscious activities of men, could be counted on to safeguard mankind against future hazards

From this it doesn't seem surprising that smart people would have initially seen something like communism as the next step in the inevitable moral and social progress of humanity, powered by reason. Combine this high prior that communism would be good with lack of strong evidence of communism's problems (it probably looked pretty good from the outside, and any unfavorable info that did leak out, you couldn't be sure wasn't anti-communist propaganda)... and you almost don't need to invoke human irrationality to explain them being enamored with communism.

Maybe a more distal cause is that the Enlightenment was too successful, in that the values it settled upon through "reason", like freedom and democracy, turned out to work pretty well (relative to the old norms), which made people trust reason and progress too much, when in retrospect, the Enlightenment philosophers seem to have just gotten lucky [LW(p) · GW(p)]. (Or maybe there are some deeper explanations than "luck" for why they were right, but it sure doesn't seem to have much to do with their explicit reasoning.)

This book has an interesting discussion about this phenomenon,

When reading the accounts of socialist pilgrims, one cannot help wondering how so many highly educated, highly intelligent, well-informed and well-meaning people can be so colossally and persistently wrong. Of course most of us are not experts on the economy, political system or social structures of a foreign country, and it is easy for an outside observer to come up with a wrong assessment. But socialist pilgrims were not just wrong in the way in which, say, a finance journalist who mistakes a short-lived boom for a genuine increase in prosperity, is wrong. Those pilgrims travelled to some of the most hellish places in the world and came back convinced that they had seen paradise.

Read chapter 10 for their explanation.

But how could that be?

Shockingly easy: there was no information coming in and out of Russia that wasn't via courier (even mail was unreliable). The only way for information to get out was for someone to see something, and then survive leaving, and then tell people about it.

Also keep in mind the context: absolute monarchies routinely have bloody rebellions and purges; revolutions and civil wars are usually extended and bloody affairs. It wasn't until Lenin died and Stalin took over that it became clear a relatively stable government was murdering lots of people for increasingly bizarre reasons.

Fully agree. Just created this account to chime in on how strange it appears for the author to describe someone as a ’polymath genius’ in biochemistry and sinology and to then claim that said individual was supposedly duped on a subject concerning biochemistry by a group of humans in the culture he most intensively studied.

It’s far more likely that the author himself was duped on this matter. (Along with the subset of the population less well informed than Needham, which is to say nearly everyone that superficially looked into the issue from a pro-American perspective )

Haldane wanted children but may have been infertile due to injuries suffered in WW1. IIRC Needham and his wife may also have had fertility issues. 

I think Cambridge was much stronger than Oxford in STEM and philosophy until after WW2. Schrödinger was briefly at Oxford but they objected to his desire to live with both his wife and mistress. Outside of STEM, there was Tolkien, CS Lewis, and TE Lawrence.

Julian and Aldous Huxley were at Oxford and mixed with Haldane and Needham for sure. Haldane was an undergrad at Oxford and his dad a professor. 

Yes, I know less about Ramsey's life, but he was an incredible talent and interacted with Wittgenstein and Keynes. Paul Dirac and Ronald Fisher also spent part of their careers at Cambridge in this period but I know less about their lives. (There's also G. H. Hardy). 

Keynes's involvement with the Versailles Peace Conference is quite well known. Russell was a famous public intellectual after leaving academia but I think is now better known for his earlier work in the foundations of mathematics and philosophy. Turing's codebreaking work is also well known.

I know less about Keynes. Feel free to suggest some.

I mentioned Ramsey in an another comment. Very brilliant polymath and likely would be included if he'd lived longer. 

Dennett talks about Darwin’s theory of evolution being a “universal acid” that flowed everywhere, dissolved many incorrect things, and left everything we ‘thought’ we knew forever changed. Wittgenstein’s Philosophical Investigations, with its description of language-games and the strong thesis that this is actually the only thing language is, was that for philosophy. Before PI it was reasonable to think that words have intrinsic meanings; after, it wasn’t.

Is this a rhetorical question? What kind of evidence are you looking for? 

At this point, it's more efficient to learn about Wittgenstein's contributions by reading more recent works. If you wanted some intro material on Wittgenstein's own work, you could try SEP, Grayling, or Soames [detailed historical development of analytic philosophy] but I haven't looked at these myself.  Also any discussions by Dennett of Wittgenstein on philosophy of mind, Kripke (or McGinn's discussion) on Wittgenstein on rule-following, discussion of family resemblance for concepts in various works.