Too often I see history books with arguments of the nature: “x also shaped y.” They are usually written like this: “Early Virginian society was not only shaped by economics but also by gender relations” or “the American Civil War also had international impact.”
I respond typically by uttering “that is not a thesis”, as I close the book and throw it on the pile of books on my table.
It amazes me to no end that peer-reviewed books can get away with having a thesis on this kind.
I cannot say it clear enough: a sentence of that type does not rise to the level of historical explanation. Historians are concerned with knowing not only that X had an effect on Y, but how much effect X had on Y.
In my book, Creative Historical Thinking, I include a chapter on the history of “why men stopped wearing hats” which directly address this problem of insufficient thesis statements, and the problem of disaggregating multiple factors of a historical explanation.
There are many possible reasons why men stopped wearing hats: more time spent indoors and in automobiles, the invention of sunglasses, decrease of hierarchical society marked by particular clothes, and on and on. (to see a longer list consult chapter nine in my book).
The task of the historian is to render the complexities of the past into an understandable narrative or analysis. A historian who says “everything” or “nothing” caused men to stop wearing hats is not accurately said to be a historian, since she is not providing explanation. Nor is stating causal factors sufficient for establishing a historical thesis. A thesis must explain not only that x shaped y, but to what extent x shaped y, and how, why, where (etc.) this happened.
Beware the thesis that does not rise to this level of explanation, for it is not properly called a thesis if it does not provide explanation of the cause of the effect.