The pledge by Mark Zuckerberg, the founder of Facebook, and his wife Priscilla Chan, to give at least $3bn over the next decade for medical research has justifiably received large numbers of “likes”, “loves” and “wows” on his social media site. It needs just a little nuance.

The couple have every right to spend their fortune how they wish. Choosing philanthropy over personal luxury is admirable. It sets a powerful example for others to follow in donating money, expertise and time — from fellow billionaires, companies and individuals with far more modest means.

The focus on medical research is also an excellent priority with global impact and high potential benefits. Ill health causes vast amounts of suffering, while disease and premature death are brakes on social and economic development around the world.