"Yes we can and do". I'm afraid that is not true and cannot possibly be true, and a moments thought should confirm that..

Whether we are historians or journalists or random members of the human race all we know and all we can know is what some people wrote and what some people said. We haven't even got the kind of suggestive evidence that social research and opinion polls and suchlike can gather about contemporary public opinion which can allow us to make tentative generalisations.