Watching the rise of Donald Trump, the success of anti-immigrant Brexiters, the callous demonisation of refugees in Australia and elsewhere, it’s understandable to be outraged.

These are human beings, deserving of at least that level of respect. But this isn’t an argument that can be fought on moral grounds. It never has been.

The rise of populists and anti-immigration movements is motivated, in large part, by genuine fear. Australians are seeing record low wage growth, Americans are seeing similar real wage stagnation, and other nations are too. Meanwhile, the European unemployment rate is heading in the right direction, but is still shockingly high, especially in some states, leaving the spectre of a lost generation. And all of this is against the backdrop of the largest technological shift since the industrial revolution.

With this context it’s understandable that millions of refugees look less than appealing. That the other, especially an easily demonised other, is feeling the brunt. People are genuinely worried about putting food on the table, for their futures and children — let’s not go into zero-sum thinking fostered by our politicians and education systems.

The point is, this isn’t a debate you can tackle with “well, it’s the least we can do”. You need an equally self-interested argument. And I may have found one.

I’ve just finished the first chapter of The Geography of Genius, a splendidly written first-person investigation of the connection between place and ideas. The author, Eric Weiner, is a long-time foreign correspondent and travel writer, so you can imagine the beautiful language and imagery.

Anyway, the first chapter is an investigation of ancient Athens. Why was this one place the progenitor of so much we take for granted — art, science, finance, literature, philosophy, and politics etc.? This is especially remarkable given the short span of Athen’s golden age, and that it wasn’t the richest or biggest of the Greek states.

The Athenians were particularly creative — dare I say, innovative. And the reason why comes back to something I’ve written about before — they had a lot of raw material. Athens was an incredibly open place, it’s people travelling widely, and, extraordinarily for the time, foreigners were allowed to come and thrive. All of these influences came together and mixed, illustrating deficiencies not immediately apparent to locals, surfacing solutions from far and wide.

“The ancient Greeks didn’t invent much at all. They were, in fact, tremendous moochers. They borrowed the alphabet from the Phoenicians, medicine and sculpture from the Egyptians, mathematics from the Babylonians, literature from the Sumerians. They felt no shame in their intellectual pilfering. The Athenians, for all their many flaws (see slavery and treatment of women), didn’t suffer from the Not Invented Here complex.”

“This willingness to borrow, steal, and embellish distinguished Athens from its neighbors. Athenians were more open to foreign ideas and, in the final analysis, more open-minded. At the symposia, they enjoyed the poetry of outsiders as much as that of locals. They incorporated many foreign words into their vocabulary and even began wearing foreign clothes. Athens was both Greek and foreign, in much the way that New York is an American city and not.”

At one point, Weiner very clearly links this openness and cross-pollination to commerce. Something we can see in some of today’s more interesting technology companies — Transferwise, WhatsApp, and Telegram were all founded by immigrants and exiles, largely solving problems not evident in their new homes. Nevertheless, they bring an incredible amount of wealth and expertise. Would any of these countries be better for locking them out?

The reverse example is also present, as evidenced by Facebook’s spectacular failure to bring Free Basics to India, largely thanks to a lack of cultural awareness. Diversity is an incredibly powerful facet in the creation and dissemination of ideas. Even if you don’t immediately benefit from the diversity, you may do so indirectly — you might not get a job with Facebook, but your life is undoubtedly richer from greater access to friends and family.

“The Athenians, master shipbuilders and sailors, journeyed to Egypt, Mesopotamia, and beyond and brought back every good imaginable. Embedded in those goods were some stowaways: ideas.”

“Ideas insert themselves into the fiber of merchandise and lie dormant until a careful observer unlocks them. This is why authoritarian regimes that believe they can open their economies but not their politics are fooling themselves. It may take a while, but eventually these subversive ideas, embedded in a can of tomato soup or a pair of Crocs, squirm free.”

One of my favourite classes during university was a history of China, a central theme being the country’s cycles of expansion and isolation, and the accompanying booms and busts. Similarly, it can be argued that much of America’s success over the past hundred years comes from its immigration policy, its openness. Its being built on an idea, rather than a foundation of race, ethnicity or religion. We have so much evidence that openness works, that closing doors is nothing more than self harm.

Unfortunately, much of these issues are viewed through a zero-sum lens. Each additional immigrant is feared as a source of more competition, rather than for any of the number of benefits they provide. As fellow consumers, helping to foster demand and bring economies of scale. As more-mobile workers, smoothing out booms and busts throughout he country. And, maybe more importantly, as a source of diversity, helping us plug gaps, learn from the countless natural experiments going on, and enriching our culture. Taking in more refugees and immigrants isn’t just a moral concern, we are all the beneficiaries of millennia of mixing cultures.