A five-minute conversation has the potential to prevent 40 lives being lost. That's about how long it takes to explain the basic precepts of the Giving What We Can pledge to someone.

"I give 10% of my income to charities like Against Malaria Foundation; they use that money in cost-effective ways to prevent (e.g.) malaria in children; if I do that for every year of my working life, then on an average wage I can expect to avert 40 deaths."

That takes about 30 seconds to say out loud. Explaining the meaning of cost-effectiveness can take another minute; explaining how charities are evaluated, another minute; explaining how you calculate you'll avert 40 deaths, one more minute.

Another minute should be spent explaining that rather than ‘averting 40 deaths’ you'd expect, on a full-time median UK or US wage, to donate enough to buy 55,200 bednets, contributing to the protection of about 99,340 people and averting the deaths of about 70 children over the course of your working life and that there is considerable uncertainty in each figure, but the bottom line is that this is the best-evidenced, most-likely-to-be-highly-effective-and-do-the-most-good intervention your money can buy that we know of.

This blog does a wonderful job of explaining how to accurately tell someone exactly how their donation will do the good it does. In this article I am going to abbreviate the truth by saying I expect to avert about 40 deaths in my lifetime.

Ok, now we've up to four and half minutes, which allows time for questions. After this your friend may well take the pledge: 22% of pledge-takers do so after encountering the idea from their friends.

Even with the above qualifications and explications, it is an extraordinary fact: simply opening your mouth and talking could save 40 people's lives.

Here's the rub: talking about the pledge, or about Giving What We Can generally, can be difficult. There seem to be two main barriers. First, we're inhibited, and in fact there are lots of good reasons to be. I think the reasons to become de-inhibited are a lot more compelling, but first we're going to have to look square at those reasons for being inhibited and deal with them. After that I'll breach the second barrier: even if we're keen to talk, it can be difficult to know what to say.

I'll share with you now what may be some reasons for being inhibited. Be warned that this will be somewhat subjective, as I have gone within, as it were, to locate these thoughts; but I'm not that weird (at least on a universal scale) so possibly you will find that something resonates.

One source of inhibition may be a concern not to use your friends as means to an end. It is one of the basic conditions of friendship that we don't use our friends to achieve things that aren't necessarily in their interest. People who do so are called users and are universally reviled. Talking about GWWC could be discerned as "using" your friend since it isn't necessarily in their best interest to learn they can do more good giving their money away than by keeping it. The impression is that people in some remote place will benefit at your friend's expense, with their new bednets or deworming tablets; you in turn will feel good, again at your friend's expense; so that makes you, in the short term, a user, because you are burdening your friend to achieve some other goal.

This aspect of burdening your friend is another source of inhibition, I think. There is good evidence that, long term, giving 10% of your income to charity won’t make your friend unhappy; in fact it is likely to increase her happiness because making a genuine difference in the world (and knowing it) feels good, and we can prove that, as you can watch below. But short-term this information about effective giving is sometimes hard to hear, especially if you don’t bring up the subject in a sensitive way.

Embedded content: https://www.youtube.com/watch?v=liHWdsLEzyU

In the worst case, talking about effective giving can raise feelings of guilt, an unwelcome sense of privilege, a sense of pressure to live up to high standards. Ignorance is bliss; it can't be evaded that you your friend might not want to hear about GWWC. It may be outweighed, morally speaking, by the potential feelings of accomplishment and pride later should they pledge. But remember, they may not pledge. I'll come back to this concern about making your friends uncomfortable later.

Another source of inhibition may be the desire not to appear superior to your friends: "I give 10% of my money to effective charities. What do you do?" If friendship is fundamentally predicated on equality then by being a member of Giving What We Can you may be upsetting that balance by doing overwhelmingly more good for others than they do. Nobody wants their friends to think they’re smug or boastful. I'll come back to this too.

The final problem may be the passion many of us feel about effective giving. Expressing passion can be awkward. Generally it is thought best not to discuss religion or politics and GWWC has something of the flavour of a religion in that pledging is often motivated by the same strong feelings of universal love and a belief in the possibility of salvation. At a party, religious fervour and starry-eyed passion is not everyone's favourite cocktail.

Those are the problems, as far as I can tell. What can be done? It could be argued – but I'm not going to – that even if you are making your friends initially uncomfortable in telling them about the pledge, and causing yourself some unpleasant awkwardness, this is vastly outweighed by the good you are doing by potentially saving 40 lives. Much as there may be weight to this argument, I don't want to start treating my friends in a utilitarian way, though I like utilitarianism in theory.

I don't need to be utilitarian however. All the above inhibitions are trumped by a more fundamental predicate of friendship: honesty. You can't have a good friendship if you hide your true beliefs or feelings, including about effective giving. Friends share things with each other; if there is something you strongly believe in, they deserve to know.

That's fine then. And how do you avoid appearing superior? Well, simply because you aren't. You simply have beliefs, which by that token are as worthy of presumptive validity and as worthy of discussion as anyone else's. One of the main strengths of effective altruism is it’s non-dogmatism; everything we do is evidence-based, and we’re aware of the fact that there isn’t really any absolutely 100% concrete way to rank charities so we’re open to any new ideas. Drawing on that non-dogmatic character allows us to bring due humility with us into any discussion about pledging.

Thus you are now completely de-inhibited (and even if you aren't the line I've followed here should generally help: go into yourself, analyse your own grounds for being inhibited, and evaluate them. If you see they are without good reason they should go.)

So, let's say you are now completely de-inhibited and want to talk about the pledge. What's next? What do you say?

It's not so difficult. We like to talk about what we do. So if you are reading a book or blog about effective altruism, or have gone to a stimulating GWWC talk, or have done some fundraising for the Schistosomiasis Control Initiative, or done volunteer work with a local chapter, all of these worthy subjects can be answers to the question, 'What've you been up to?' (I advise you to practice saying "schistosomiasis” - it’s “SHIST-oh-so-MY-ass-iss”, if you’re wondering). I find myself talking about effective giving and pledging when people bring up the subject of charity, which people do surprisingly often; and people seem to appreciate my input, because it is apposite. It is a question of recognising the cues and opportunities when they arise. This is easy to do once you start watching for them.

Once the conversation starts, focus on the positive. Present donating as an opportunity rather than an obligation; reveal that giving is a source of much happiness to you; emphasise how good the good charities are and don't waste breath describing the dreadfulness of the so-called "bad" ones (remember that half of what Giving What We Can does is tries to persuade people to give at all, and in the overwhelming majority of cases, any giving is better than none).

Listen, since the best conversations are usually not monologues. Do your best to raise and discuss views antithetical to your own. Refrain from ranting, cajoling, pressuring and pontificating. And if you are bringing too much passion to the table? Then go ahead and express that passion. Ignore what I said earlier. Life is too interesting to be expressed in monotone. Do all these things and everyone will be happy.

This is but a brief resumé. There are a large amount of resources here on how to approach the conversation, including what to say should your friends balk at the magnitude of giving 10%. I recommend checking them out.

In summary: tell your friends about Giving What We Can. They will thank you for it. Your friends are interested in what interests you. In a spirit of openness, honesty and general good-naturedness, reveal to them that remarkable fact: we're capable of radically altering the lives of others for the better. A fine thing to know and a fine secret to let other people in on.