In recent years, the discussion about identity has flared up nearly everywhere in Europe. The then princess Maxima, the wife of the Dutch crown prince, got into hot water when she made the claim, in 2007, that there was no such thing as a Dutch identity. The True Finns are the third-largest party in the Finnish parliament. Belgium is being torn apart by Flemish nationalism, and elsewhere in Europe nationalist political groups are gaining ground.

There is a straightforward explanation: confrontation with different identities, in the form of immigrants and asylum-seekers, and thus confrontation with different norms and values, creates uncertainty. Identity is not the abstract quality we vaguely assume it to be: we determine our identity by placing it alongside and, increasingly, contrasting it with other possible identities. Whereas identity used to be informed by predominantly local stereotypes (as in, Belgians versus the Dutch, or the English versus the Scots), current stereotypes have become globalised and socioeconomic: it’s now the indigenous population versus ethnic minorities, ‘our’ Judaeo-Christian culture versus ‘backward’ Islam, or the ‘hard-working middle classes’ versus ‘scroungers’.

The various stereotypes have one thing in common: they serve to make us feel superior. We are more civilised, more intelligent, work harder, and so on. In the mid-20th century, the Germans looked down on the Untermenschen, the Japanese looked down on the Chinese, the French looked down on the Maghrebis — the list is endless.

Such classifications are almost always linked to external characteristics (such as skin colour, physique, and clothing), which can then be deployed in a naive debate on integration, culminating in proposals to ban headscarves (or in imposing a ‘head-rag tax’, as suggested by the populist Dutch politician Geert Wilders). Conversely, if the differences aren’t sufficiently visible, we fix that (by demanding the wearing of a Star of David, or the bearing of passports stating the holder’s race). The importance we attach to these external characteristics is a measure of our own uncertainty: remove them, and the distinctions become practically invisible. Identity is internal.

This makes it a lot harder to study; we really want to see those differences. In the present age, when explanations for all human behaviour are sought in the interplay of genes and neurons, one might expect to look there for more light to be shed on the internal aspects of identity. As usual, we forget that this was tried a century ago, using craniometry — measuring skull circumference and capacity — to establish nice, clear distinctions between races and their identities. A taboo now lies on such research, a legacy of fascism, when Nazi scientists attempted to define ‘race’ along such lines. Whatever the case, the conviction that identity can be found somewhere inside us has proved to be extremely persistent.

I take a completely different view. If we want to understand the nature of identity, we need to approach it by a different route; not in the timeless depths of our genes and brains, but in the flickering screen of the outside world, which acts as a constant mirror of identity. So the best thing is to start with the equally timeless question of who we really are.