There is no shift. The question of whether individuals are primary influence on events or whether things are "in the air" and thus almost bound to happen (albeit caused by some individual or other) has been kicked around for at least a couple centuries. Napoleon was one of early examples often used. Was he a unique individual who exerted enormous influence on course of world events? Certainly. Were conditions in the world ripe for an individual to exert forces like Napoleon did, and would someone like Napoleon have arisen if Napoleon had never been born? Also, perhaps, yes.

Evidence for the "in the air" version clearly exists in science and mathematics, where progress leads a certain direction, then a particular individual is the one who makes big advance or discovery. Often more than one person is independently making the same advance at the same time. Think of Newton and Leibniz, who independently and at same time developed calculus. Or Darwin and Alfred Russel Wallace, same thing with theory of evolution. All of these guys did extremely impressive things. But do you really think nobody else would have developed calculus or discovered evolution if these guys had all died in childbirth?

I'm not saying all advancements are 100% "in the air" and that individuals basically do nothing. But, certainly, for many of these individuals -- who we (rightfully) revere -- the same advancements (or discoveries, or destruction, or whatever) would have been accomplished by someone else if they had never been born.

Right, but the conditions being ripe for a Naploean still requires Napolean. Saying that "the time was such that someone like so and so HAD to rise up" is meaningless. Nothing HAS to happen, in the realms of human behavior. People may be likely to do something, or the potential to do a great thing might be more potent at one point in time than another, but that potency still requires an efficient cause to become real. People with vision and talent and will can, and do, and have been changing the world.

If you're interested in a smarter man than me going on about this idea, I suggest you read the Foundation series by Issac Asimov.

Perhaps the conditions being ripe for Napoleon require a Napoleank not the Napolean, which is the crux of this individual vs circumstances debate. The interesting question is whether Napoleon (or Hitler or Stalin) was a unique individual necessary for the progression of events we call history or could that role have been fulfilled by another narcissistic, paranoid egomaniac (which Napolean, Hitler, and Stalin arguably were)? Was it fate, random chance, or is it a case of the nature of those randomly in power deciding the destiny of all? We'll probably never know.

Yeah, kind of undecidable, in similar way to nature vs. nurture debate. However, I would say that the case for scientific advancements being "in the air" and nearly inevitable is much stronger than, say, the inevitability of a paranoid egomaniac arising as a leader, rather than a more even-keeled and humane figure. Political action often seems balanced to go either way, for ill or for good, while scientific progress is in comparison mostly in a single direction, onward and upward.

I'd say that the case of scientific, as well as technological 'advancements being "in the air" and nearly inevitable' is much stronger than individuals effecting social changes. For example, Reformation happened not because of Martin Luther per se, but because of printing press that gave common people the Bible, and that spread the Luther's theses around Germany in a matter of weeks, and around the world in a matter of months (arguably, this was one of the first cases of pre-Internet outrage). If you were to remove Luther, a similar movement would likely start anyway, given that it was actually growing elsewhere in parallel! People we name and attribute changes to seem to be just puppets of the circumstances.

EDIT

Scott Alexander covers that one too:

http://slatestarcodex.com/2013/03/07/we-wrestle-not-with-fle...

The conditions require someone like Napoleon to be there, which probably applies to many people. The first one to rise up usually wins. You can see it actually pretty clearly in science - multiple independent discoveries are more common than not, leading to the conclusion that if you were to kill Einstein in 1904, somebody would have published about relativity and photoelectric effect within a year or three.

An idea who has time has come