Twain was wrong on his main point. He claims self-approval as the motivator for following fashions (of all sorts), but most conformity comes from trying to navigate life: we do what works for our neighbors. IBMs dress code wasn't adopted because coworkers liked the fashion, but because if you wanted to work at IBM you needed to wear the uniform. Time and interest are limited, and copying is easy.
> Do you believe that a tenth part of the people, on either side, had any rational excuse for having an opinion about the matter at all? I studied that mighty question to the bottom -- came out empty. ... We all do no end of feeling, and we mistake it for thinking. And out of it we get an aggregation which we consider a boon.
This mistakes the value of expressing an opinion or having a vote. First, there's the personal benefit of investigating and thinking something through (even if you "came out empty"). Second, there's a public benefit to encouraging people to investigate and thinking something through on their own. Third, the 'wisdom of the crowd' might be right, show us new ideas, or offer insight and wisdom.
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This essay seems related to Paul Grahams "How to Do What You Love". He wrote that when deciding what to do, we should consider what's respected by our peers.
> What you should not do, I think, is worry about the opinion of anyone beyond your friends. You shouldn't worry about prestige. Prestige is the opinion of the rest of the world. When you can ask the opinions of people whose judgement you respect, what does it add to consider the opinions of people you don't even know? [4]
> This is easy advice to give. It's hard to follow, especially when you're young. [5] Prestige is like a powerful magnet that warps even your beliefs about what you enjoy. It causes you to work not on what you like, but what you'd like to like.
http://www.paulgraham.com/love.html