There are two competing theories about how history works: the first is that it is driven by Great Men, or Great Events, which seem to come unexpectedly and randomly change the direction of everything that comes after.

The second is that history is a long unpredictable process, somewhat like digestion, and that there are general trends and themes that slowly develop, or recur cyclically, and are outside anyone's control or direction.

I've given this a lot of thought and have come to the conclusion that both these theories are correct, and simultaneously, both are wrong. After all, don't "random" and "unpredictable" mean pretty much the same thing? Or to put it another way, it all depends on the scale at which you look, or the temporal resolution you employ. I.e., both processes operate simultaneously.

Confused? I'm not surprised. I suppose the best way to look at it is the old joke:

Three historians, A German, an American, and a Chinese, are discussing the influence of Napoleon Bonaparte on history. The German says the superior man, the ubermensch, changes the course of history through his sheer strength of will. The American claims that history is the result of an infinite number of influences reacting unpredictably, and if Napoleon hadn't come along, someone else like him would have.
The Chinese philosopher merely answers "Its too early to say, one way or the other."

Still, I am an optimist. Good ideas are more likely to survive longer than bad ones, so there is some progress. Some times there are eddies in the time stream, and kinks in our timelines, but over the long run, things do get better. Its always been a "two steps forward, one back" kind of progress, but it is progress nevertheless.

I don't believe in Asimov's psychohistory, but I do believe the future will be better if we just wait long enough. I also believe that when the future gets here, it will be like nothing anyone ever anticipated.

In short, yes, it IS possible to influence the future; but you can't ever predict how its going to turn out. Napoleon, Hitler and George W Bush all changed the world, but it didn't turn out any way at all the way they expected.