Just 52 years after escaping military dictatorship, Portugal is an EU and eurozone member and the world’s seventh-safest country. While Donald Trump's systematic destruction of the rules-based global order will not reverse this progress, nor will it do any good for Portugal, the US, or anyone else.

CAMBRIDGE—Fifty years ago this month, I was in Lisbon working for the Banco de Portugal. With me were four other MIT graduate students, including the future Nobel laureate Paul Krugman. Inspired by Krugman’s reminiscences about that experience, and in light of our current geopolitical circumstances, I find myself reflecting on what we saw that summer.