I have mixed feelings about Seligman. Those three concepts are indeed useful. On the other hand, the experiments that made his name, though presumably within the standards of the time, involved treatment of dogs so cruel that it's hard to read about them without wondering what kind of person would do such things. Basically they showed that, when randomly tortured, most dogs become depressed (http://en.wikipedia.org/wiki/Learned_helplessness). Bizarrely, or perhaps naturally, these experiments turn out to have been one of the inspirations for the CIA torture program. Seligman says he had nothing to do with it, but he did have contact with the people who designed it and has declined to publicly disagree with their application of his work (http://andrewsullivan.theatlantic.com/the_daily_dish/2008/07...). This is admittedly a weak link, but a notable one.
I noted the conceptual connection between "learned optimism" and "learned helplessness", but didn't realize it was the same guy.
I want to expand on "randomly tortured" dogs. The electric shocks given weren't damaging (though they were painful), it was the lack of power over them was damaging, leaving the dogs hopelessly cowering in a corner. It wasn't the torture that harmed them, but its arbitrariness. That is, the cruelest part was not the torture itself. Knowledge can be used to harm people; but it can also be used to help them, as Dr. Seligman has subsequently done with "learned optimism".
I agree that giving electric shocks to dogs is a disturbing thing to do.
Electric shocks that were damaging would defeat the purpose of the experiment. It required a comparison between dogs that had some control over the shocks and those that didn't (though both received exactly the same shocks). If both dogs were harmed, it would be harder to differentiate the harm due to the randomness.
Of course you may doubt their reporting of their own experiments. We only have their word for it that they conducted the experiments at all.
