There is a lot of angst in the world today over differences with the potential to divide people, whether race, religion, age, income, nationality or ideology.

A Singaporean friend who now lives in London described the anger and stereotyping that went on post-Brexit, including comments like "you're white, you must have voted out", or Londoners choosing to boycott parts of the country north of the capital that opted to leave the European Union.

Over in the United States, deep distrust between blacks and whites persists in some cities, and on display too in this presidential election year are fierce battles not only between supporters of different political parties but also within the Republican party ranks and, to a lesser extent, among Democrats.

In the Middle East, parts of South Asia and Turkey, sectarian strife between people of different religions and between those who belong to different sects within a religion has descended into violence and even civil war.

That is the backdrop against which the Prime Minister decided to make unity the theme of his recent National Day message. Mr Lee Hsien Loong cited three threats to Singapore's cohesion, namely, extremist terrorism, economic disruption that affects people's jobs and their children's future, and populist politics. These threats are global in nature and powerful enough to sweep through entire populations. In their wake, individuals can feel helpless.

These are tides that accentuate differences which occur naturally in any society, and turn them into sources of rivalry and division. They cause people to feel vulnerable and afraid. They drive some to blame others for their plight and, when they do, those who look or act different become convenient targets.

And yet, people are not helpless in the face of these impersonal forces of change, and it is important that they not feel helpless. While no single human can stop terrorism or economic disruption or bad politics, every single person can play his or her part to bridge differences and lay a foundation of trust that can help hold society together in times of crisis.

It can start with something small, like a shared interest that can be built on.

For me, one of the highlights of this National Day was that I made some thosai kakis, which is to say I found some people who share my love for the Indian savoury pancake, and we made plans to go together to Ghim Moh and Serangoon Road to sample some of the best this country has to offer.

My fellow enthusiasts range in age from the mid-20s to the mid-60s. One is just starting out in his career, one is retired and two of us are mid-career. All of us are Chinese but met at a party for an Indian friend, who does not as it turns out like thosai as much as we do. At his potluck lunch party, we jockeyed to sit near the masala thosai while he had eyes only for the spare ribs done Chinese-style.

In the right setting, friendships that bridge differences of age and race can spring up from small things in common. Food is a good way to build a bridge of trust, especially when delicious enough to entice and shared in a spirit of generosity that demands nothing in return.

It reminded me of the opening paragraphs of the novel Aunt Safiyya And The Monastery by Egyptian writer Bahaa' Taher, which drew me in for this very reason. This is how it begins: "From the southernmost house in the village, it would take you about half an hour to reach the monastery on foot, and a good deal less than that on the back of a mount... Since ours was the house closest to the monastery, we were in some sense its neighbours. The monks used to give us, in season, sugared dates of a variety known for its small pits, not produced by any of the date palms in our village, but only by those found on the monastery farm.

"In my boyhood - more than thirty years ago - my father used to take me along with him on Palm Sunday and on the 7th of January - the Coptic Christmas - to offer holiday greetings to the monks. Among the boxes packed with cookies that my mother used to charge me with delivering on the occasion of our Lesser Feast (Eid) was 'the monastery's box'... she would have lined the bottom of each box with cookies sprinkled with sugar, on top of which she placed a thin layer of ghurayyiba (butter pastries flavoured with cardamom), exceptionally light and delicate, with a clove stuck into the middle of each one."

This novel tells the story of a remarkable alliance between a Muslim village in Upper Egypt and the inhabitants of a nearby Coptic monastery, a friendship between peoples of different faiths that is difficult to imagine today, when religious difference has become a source of strife in many parts of the Middle East. Taher's tale does not offer facile solutions to the forces that divide - in fact, its ending is tragic - but it is lit from within by the author's faith in people's ability to resolve differences and transcend boundaries.

This faith rests on the possibility of friendship between people who seem on the surface to be very different. Indeed, "it is in our friendships that we are most likely to recognise that... we share a common humanity that enables us to see beyond the stereotypes and, importantly, difference", observes English teacher and writer Lola Okolosie in a column in The Guardian, in which she reflects on often being the only black person in the room at gatherings hosted by her white friends in London where she lives.

Friendship matters also because, unlike state efforts to spur integration or foster unity, it does not seek to impose a particular conception of the good society from above in ways that can ignore or even stamp out differences that are not well understood or appreciated. Friendship knits unity from the bottom up, person by person.

Diversity in friendship is hard to track. The surveys that exist tend to focus on race. In 2013, for instance, the Institute of Policy Studies (IPS) and OnePeople.sg, a racial harmony advocacy group, surveyed 4,000 people on their attitudes about race. They found that while 80 per cent said they were comfortable with a friend of another race, only 46 per cent reported actually having a close friend of another race, with young people and members of minority races more likely to have close friends of another race.

Yet, diversity does not end with race. In a commentary for The Straits Times last Friday, IPS senior research fellow Mathew Mathews wrote about Singapore's new diversities. He observed that "welcoming what is new and foreign into our island has meant that Singaporeans, who have become accustomed to a set number of diversities which are neatly categorised and presented, have had to accept that these are in a state of flux".

Diversity is complex but the first step to befriending someone who seems different can involve something simple, like thosai and time to eat it together.