Every parent knows the biological intoxication — at least for a few weeks — of having your first child. That, plus living in California and being a technology idealist, may account for the somewhat sappy tone of Mark Zuckerberg’s letter this week to his new daughter Max, in which he announced that he will devote 99 per cent of his $45bn wealth to good works.

The Facebook founder’s pledge, with his wife Priscilla Chan, of “a moral responsibility to all children in the next generation” is no doubt deeply felt and genuine. It also has a coolly rational outcome — that he can demerge two things that have been mixed up in a single corporate structure: Facebook and philanthropy. The “social mission” he declared at Facebook when it went public in 2012 now has another outlet.

Warren Buffett has no higher social purpose for Berkshire Hathaway than achieving strong returns for shareholders; nor did Bill Gates for Microsoft when he was running it. The $41bn Bill & Melinda Gates Foundation, to which Mr Buffett has promised to donate much of his wealth, is their main vehicle for venture philanthropy, impact investing, or call it what you will. Like Sergey Brin and Larry Page, Google’s founders, Mr Zuckerberg has until now combined running a corporation, investing in offbeat ideas and making the world a better place. His letter to investors in Facebook’s initial public offering was more sober than this week’s missive but shared some of the same idealism, with its talk of creating “more direct empowerment of people”.