Sir, – Patrick Collison is free to spend his fortune as he chooses (“Patrick Collison gives $7m to combat US wealth tax”, July 29th), but his decision to donate millions to try to defeat a proposal to help fund healthcare is revealing.The fact that someone can spend millions in this way is itself an argument for a wealth tax. It also highlights the unhealthy reality that extreme wealth brings not just economic privilege but disproportionate political influence.At a time of severe economic and healthcare inequality, it is difficult to see Collison’s decision as anything other than another billionaire using his fortune to protect the interests of billionaires. – Yours, etcSéamus White,Bóthar na gCloch,Baile Átha Cliath 7.