There are authors unaware of this gap, and who present a Cleopatra or a soldier of Napoleon's Grande Armée as though they saw the world just like, say, a contemporary American teenager or a Green Beret. They put contemporary characters into past situations, changing little more than the wardrobe. But when you and I read historical fiction, we demand something more. We want to get into the minds of those very foreign people. People in the past just don't think and act the way we do. It's not just a question of how much they know or what tools or weapons they have available — all that is important — but, more mysteriously, the ways their brains are configured.
The biggest break between one kind of thinking and another comes, historically, with literacy. Julian Jaynes, The Origin of Consciousness in the Breakdown of the Bicameral Mind, Walter Ong, Orality and Literacy, and the pioneering work of Vygotsky and Luria in Uzbekistan and other neuroscientists and diverse scholars have made clear, the neural paths that connect and stimulate different parts of the brain change enormously with literacy. As Jaynes put it, preliteracy we used to hear voices that seemed to come from afar but were really memories stored in one hemisphere of the brain, whereas learning to read connects the two hemispheres so that one half of the brain is aware of what the other half is firing off in electrons.
But the changes don't end there. Even in a society where everyone is literate, new technologies — the telegraph, then the telephone, then TV, and on to Smartphones and Whatsapp — create new neurological connections. Our concepts of time have changed enormously, but also our sense of relationships in an era where one can suddenly acquire a zillion "friends" or even "followers" without leaving home.
In my case, in my novel in progress, I'm trying to understand and to present to readers the thinking of people who acted in — whether for or against or just trying to survive — the Paris Commune of 1871. They spoke a different language from the one I'm using, but more than that, they lived in a culture that was more oral than ours (not everybody knew how to read, and only a minority read anything at all complicated), where inner city mobility was either on foot or by horse-drawn vehicle or on horseback, and where relationships — men and women, or comrades of the same sex, or rivals — obeyed different traditions from ours.
But we must try to reach them, if we are to understand anything about the Commune and thus to understand how the western revolutionary tradition emerged and how it has changed. We can come closer to understanding if we read carefully what they themselves said about it, and the testimony left by survivors of the bloody massacre of May 1871, together with court transcripts and newspaper reports and other documents, is abundant. We can come closer, but we cannot quite reach them. So my solution, like Fowles' in The French Lieutenant's Woman, is to acknowledge the gap, to let readers know that I am aware that those people are and ever will be different from us.