Mind-killer warning: politics
The strange thing is that in the western world internalism is generally associated with conservatism and a bit of a callpous view, expecting people to bootstrap themselves, while the external view is more associated with compassion, egalitarianism, empathy, sharing and political leftism. But this is not necessarily so and I have seen evidence for it not being so.
Specifically, you can see in a lot of places in Eastern Europe people flaunting their wealth more aggressively than in Western Europe, wearing designer brands being more important and so on, clearly shaming people who look poor as unsophisticates etc. Yet the views are very external. Especially being the right place at the right time, knowing the right people, having the right connections and so on. This is something mostly everybody agrees there that they matter most. Externalist views don't lead to a lot of compassion there.
The point is, the rich in these regions knew perfectly well they don't really deserved it, they have good connections, are not super hard workers, yet it does not fuel egalitarianism, it fuels much stronger aristocratism than in the West.
I cannot 100% explain why. My best bet is power. If you need to deserve what you have, you are still one of the underpowered proles, the perfect victims who can be exploited by anyone strong. Not needing to deserve what you have is a sign of power. Showing off wealth you got not by earning it but having the right i.e. powerful connections is a demonstration of power.
The point here is, the West thinks there are only two ways of thinking, while there is in fact three. The two the West knows is either everybody baking their own pie (internalist) or everybody getting a slice from a common pie, but how big the slice is depends on power, which is bad, as it is exploitative, and it would be better to have equal power and thus equal slices. However, there is the third view, that the West is unwilling to recognize that it exists, which view is that everybody getting a slice from the common pie, how big is the pie depends on power, which means get as much power as you can, get a big slice, and then happily bathe in their sweet tears of envy ever after. This probably sounds evil. But this is incredibly common in non-Western circumstances, although of course way less directly as I presented it, I wanted to over-emphasize it a bit for shock value to make a point, but it is obviously usually far more subtle. The closest thing the West ever got to understanding this third option is the gangsta, and gangsta-rapper culture: the gold and diamonds people like 50 Cent wear are to demonstrate power, not merit.
My point is this: don't think you can make the world fairer and more compassionate or more left-wing if you manage to kill the just world fallacy! It could just as well turn more aristocratic or more gangsta-style. In the absence of explaining inequality with merit, people will not necessarily turn to equality, they may as well explain it by power, the power they have: and realize they enjoy flaunting their power around.
What do you think about these pairs of statements?
They have a similar theme: the first statement suggests that an outcome (misfortune, respect, or a good job) for a person are the result of their own action or volition. The second assigns the outcome to some external factor like bad luck.(1)
People who tend to think their own attitudes or efforts can control what happens to them are said to have an internal locus of control, those who don't, an external locus of control. (Call them 'internals' and 'externals' for short).
Internals seem to do better at life, pace obvious confounding: maybe instead of internals doing better by virtue of their internal locus of control, being successful inclines you to attribute success internal factors and so become more internal, and vice versa if you fail.(2) If you don't think the relationship is wholly confounded, then there is some prudential benefit for becoming more internal.
Yet internal versus external is not just a matter of taste, but a factual claim about the world. Do people, in general, get what their actions deserve, or is it generally thanks to matters outside their control?
Why the external view is right
Here are some reasons in favour of an external view:(3)
On cursory examination the contours of how our lives are turned out are set by factors outside our control, merely by where we are born and who our parents are. Even after this we know various predictors, similarly outside (or mostly outside) of our control, that exert their effects on how our lives turn out: IQ is one, but we could throw in personality traits, mental health, height, attractiveness, etc.
So the answer to 'What determined how I turned out, compared to everyone else on the planet?', the answer surely has to by primarily about external factors, and our internal drive or will is relegated a long way down the list. Even if we want to look at narrower questions, like "What has made me turn out the way I am, versus all the other people who were likewise born in rich countries in comfortable circumstances?" It is still unclear whether the locus of control resides within our will: perhaps a combination of our IQ, height, gender, race, risk of mental illness and so on will still do the bulk of the explanatory work.(4)
Bringing the true and the prudentially rational together again
If it is the case that folks with an internal locus of control succeed more, yet also the external view being generally closer to the truth of the matter, this is unfortunate. What is true and what is prudentially rational seem to be diverging, such that it might be in your interests not to know about the evidence in support of an external locus of control view, as deluding yourself about an internal locus of control view would lead to your greater success.
Yet it is generally better not to believe falsehoods. Further, the internal view may have some costs. One possibility is fueling a just world fallacy: if one thinks that outcomes are generally internally controlled, then a corollary is when bad things happen to someone or they fail at something, it was primarily their fault rather than them being a victim of circumstance.
So what next? Perhaps the right view is to say that: although most important things are outside our control, not everything is. Insofar as we do the best with what things we can control, we make our lives go better. And the scope of internal factors - albeit conditional on being a rich westerner etc. - may be quite large: it might determine whether you get through medical school, publish a paper, or put in enough work to do justice to your talents. All are worth doing.
Acknowledgements
Inspired by Amanda MacAskill's remarks, and in partial response of Peter McIntyre. Neither are responsible for what I've written, and the former's agreement or the latter's disagreement with this post shouldn't be assumed.
1) Some ground-clearing: free will can begin to loom large here - after all, maybe my actions are just a result of my brain's particular physical state, and my brain's particular physical state at t depends on it's state at t-1, and so on and so forth all the way to the big bang. If so, there is no 'internal willer' for my internal locus of control to reside.
However, even if that is so, we can parse things in a compatibilist way: 'internal' factors are those which my choices can affect; external factors are those which my choices cannot affect. "Time spent training" is an internal factor as to how fast I can run, as (borrowing Hume), if I wanted to spend more time training, I could spend more time training, and vice versa. In contrast, "Hemiparesis secondary to birth injury" is an external factor, as I had no control over whether it happened to me, and no means of reversing it now. So the first set of answers imply support for the results of our choices being more important; whilst the second set assign more weight to things 'outside our control'.
2) In fairness, there's a pretty good story as to why there should be 'forward action': in the cases where outcome is a mix of 'luck' factors (which are a given to anyone), and 'volitional ones' (which are malleable), people inclined to think the internal ones matter a lot will work hard at them, and so will do better when this is mixed in with the external determinants.
3) This ignores edge cases where we can clearly see the external factors dominate - e.g. getting childhood leukaemia, getting struck by lightning etc. - I guess sensible proponents of an internal locus of control would say that there will be cases like this, but for most people, in most cases, their destiny is in their hands. Hence I focus on population level factors.
4) Ironically, one may wonder to what extent having an internal versus external view is itself an external factor.