The Globe and Mail reports in its Thursday edition that tariff imposition stems from mercantilist thinking, dominant 300 years ago along with witch burning, blood leeching and chamber pots. Guest columnist Ken Fisher writes that enter wacky "Liberation Day" with bigger, broader and more foolishly fashioned tariffs than previously imaginable, underpinned by mind-numbing economic misperceptions and moronic math. While U.S. President Donald Trump's 10-per-cent universal levies and far steeper "reciprocal" tariffs skipped Canada, the Toronto Stock Exchange still tumbled alongside global stocks as uncertainty skyrocketed. Trade balances alone are not predictors of economic success. They are non-cash-flow accounting measures. Even if all his dumb tariffs return, the effect should prove smaller than feared -- which is bullish. Tariffs have to be collected. The subportion of U.S. Customs that does that work is understaffed, with only 2,500 employees and outdated technology. Then come legal challenges. Mr. Trump's universal tariffs are almost surely unconstitutional, violating the "national emergency" ground rules he used to impose them without the required previous Congress okay. Selling in and around panics is ultrafoolish.