Hmm, that’s a very tricky question. Early medieval historians recently had a pretty heated debate over the role of ethnicity in creating common identity. Things got quite unpleasant, but it ended up leading to a really interesting book: Andrew Gillett (ed.) 2002 On Barbarian Identity.

Although the contributing authors argued about many things, most of them took it for granted that identity is something constructed through practice. They agreed that identity isn’t who we are; it’s what we do. Even if my grandparents spoke a Germanic language and grew up on the far side of the Rhine, if I join the Roman army and adopt a Roman name, I’m effectively a Roman. Or if my parents had me baptized at St Albans in England, I might still choose to adopt the paganism of my new Anglo-Saxon neighbors. That is, in a nutshell, how the practice theory works with regard to identity.

The main problem that historians debated was just how free we are to choose our identities: sure I can adopt a Roman name, but what if absolutely everyone knows my parents were Goths? Can that ever be forgotten? And it’s in these situations of difference that medieval historians can best make sense of identity: it’s about contrasts. So in early medieval Europe, all these migrating groups took on ethnic names. That tells us that they thought ethnicity was one of the most important dimensions of identity. (As opposed to “Roman,” which was a civic, not an ethnic, identity.) Or in late medieval Spain, Jews, Muslims, and Christians repeatedly engaged in religious debates. That tells us that they thought religion was one of the most important aspects of identity.

However, if you were an “uneducated random peasant” living in a society that baptizes all its babies and gives a churchyard burial to all its dead, then calling yourself a Christian won’t give you much of a sense of identity -- it’ll make you feel just like everyone else. But when the bishop passes by draped in his silks, carrying his shepherd’s crook plated in gold and encrusted with gems, you might start thinking about the very real material differences that separate your worlds. Or when you visit the market to sell off your surplus, you might wonder at the monk recording the bishop’s tithe with parchment and quill, asking yourself what kind of person requires more than a farmer’s spoken oath. Or when you share a pint with the shepherd come down from the hills, you might ask yourself what drives such a man to live without the regular comforts of hearth and home. Conversely, if you’re the visiting merchant traveling with a caravan of people who were raised in different places, speaking different languages, and worshiping different gods, you might wonder at the bland monotony of these one-god, one-language, sedentary townsfolk who all blend into one.

In short, ethnicity, language, religion, birthplace, social status, degree of wealth, manner of living, and education were all dimensions of identity available to medieval people. These people were every bit as creative and diverse in their identities as we are today, having favorite sports, favorite music, favorite foods, and subtle differences of speech, thought, and actions. Most of these things would have gone unnoticed and seemed irrelevant in daily living, irrelevant that is, until you met someone who was decidedly different from you, leaving you to puzzle over what it was that made those differences, what it was that gave you your individual identity.

So there’s no easy answer, but it’s important to remember that Christianity was no more uniform in the middle ages than it is today -- all sorts of different people were Christians, and even the same sorts of people might practice Christianity differently.