The New York Post reports that President Trump plans to confront NATO partners over what he calls 'funny math' on defense spending — creative accounting that makes a budget look compliant while the actual outlays fall short. Some of the alliance's most prominent members, the paper notes, are struggling to reach even the minimum goal set for 2030. I confess this particular arithmetic problem is not new to me. I watched colonial assemblies issue paper promises against revenues that did not yet exist, and I watched working people receive those promises at face value before discovering they were worth rather less.

A pledge is a bill of exchange drawn on the future. It is perfectly legitimate — I issued enough of them in my printing days — but only so long as the drawer has the means and the intention to honor it. When a nation announces a defense commitment of two percent of its output and then reports 'one-and-a-half percent plus certain pension costs plus depreciation on kit purchased in 1987,' it is not meeting its obligation. It is redescribing it. The partners who do pay full freight are, in effect, subsidizing the ones who do not, and the working taxpayer in the paying country bears that burden without being asked.

I spent years in diplomatic service — in London, in Paris — and I know that allies are not charities. They are arrangements of mutual interest, and mutual interest requires mutual contribution, honestly measured. A common defense is precisely like a common drainage ditch in a Philadelphia neighborhood: if some householders dig their share and some merely stand by and watch, the ditch is dug anyway, but the resentment that follows poisons the neighborhood for a generation. (Inference: the political cost of perceived free-riding within alliances tends to outlast any single summit.)

That said, I would counsel against the habit of measuring virtue solely by the size of a military budget. A nation that spends heavily on arms while its roads crumble, its courts are corrupted, and its people are poorly schooled has not bought security — it has bought an expensive illusion. The composition of the spending matters alongside the quantity. NATO partners arguing over percentage points might also ask whether the money pledged is purchasing genuine capability or simply feeding the habits of a peacetime bureaucracy. On that question, the National Review's parallel piece on Pentagon transformation — which I note but decline to colonize — raises a concern worth any alliance member's attention.

My practical counsel to the citizen watching this summit unfold: do not let the large numbers — two percent of a national product running into the trillions — obscure the personal arithmetic. Defense commitments unpaid by governments are ultimately paid by taxpayers, either through higher levies on the honest or through the slow tax of inflation on those who hold the currency. Ask your representative not merely whether your country has 'signed on' to a target, but whether the appropriations committees have actually funded it. A promise written in a communiqué is worth no more than paper money without backing — which is to say, precisely as much as the people behind it choose to honor.