I think history is not truly knowable. Historical facts are knowable. Hypotheticals have no role in history because they completely alter the weave of history. Once you move into motivations they we can only presume. That is one of the very interesting aspects of history. Why does a historical figure make the choice they do, would I have made that choice? This is one of the aspects of BHP I enjoy, Jamie's foray into the mind of the figures. History is also about perspective. What would the Vikings have to say? Ask the Scots and Welsh about this history and your version will be different. History can be seen as summation of every single persons choices and actions. A tipping point is reached and major events occur. Great men play a disproportionate role, whether they rose on their own or were products of their time /culture; once they attain a point of leverage or action then they influence events strongly. I suppose one could generate a great idea theory of history where great ideas move history, for example: the worth of the individual or the belief in one God, freedom of worship or one man one vote. People jump onto the ideas and we get to the tipping point again and something big happens. Get great men together with great ideas then watch out. We each choose how we see history.