Optimists tend to look for method in US President Donald Trump’s apparent madness. For once, I’m inclined to agree.

From a distance, Trump’s lashing out against Canadian Prime Minister Justin Trudeau on Twitter seems like more of the President's characteristic lunacy. Despite supposedly talking tough on steel and aluminium tariffs in his post-G7 summit press conference, Trudeau didn’t announce anything the US didn’t already expect. The US has so far refused to exempt Canada from its tariffs, and Canada had clearly signalled that it would retaliate.