The death of Mario Cuomo takes from us not only one of history’s most eloquent liberals but also one who was surprisingly friendly to conservatives. It was one of Cuomo’s oddest — and from our point of view, most wonderful — traits. He had an angry streak, no doubt, and he never had any truck with governing conservatives. But we had the sense that he enjoyed, even envied, the profusion of ideas that burst forth on the right in the 1970s, triumphed during the Reagan years, and has flowered ever since.

We first met Cuomo at a dinner party at, of all places, the Manhattan home of William F. Buckley. We didn’t know either of them particularly well. So we were startled when we emerged from the entry way (past the famous harpsichord) and turned into the living room to discover Cuomo and Buckley sitting together on the couch in warm and earnest conversation. About what we don’t know. But here were New York’s most famous conservative and its most famous liberal almost — we don’t want to suggest anything salacious here — politically necking.

Even those who knew them well, we soon discovered, marveled at their friendship. And we soon learned that it wasn’t just Buckley. Cuomo was one of the first guests at a sitting of the editorial board of The New York Sun and was full of enthusiasm for the idea of a right-of-center broadsheet in the city he loved so much. We never did find much common ground politically. But we appreciated more than he might have guessed his encouragement and the several lunches shared, letters exchanged, and the occasional jousting in the editorial columns of the Sun.

Our favorite exchange was over the Iraq War — and, on a key point of constitutionalism, we’ve come to the view that Cuomo had the better part of the argument. It erupted over our editorial “‘I Didn’t Have an Answer’,” which was issued in May 2007 when it looked like a faction of the Republican Party was turning against President Bush in respect of he war. The editorial told the story of how President Lincoln had shamed his supporters in Illinois, who didn’t want to answer a new draft call. Any suggestion that Bush and Lincoln wore the same boots, so to speak, outraged Cuomo.

We learned this in a phone from one of Cuomo’s cronies, Lincoln scholar Harold Holzer, who telephoned to warn us that we might be hearing from the former governor, who was apoplectic over the editorial. This resulted in the publication of the longest letter-to-the-editor ever issued in the Sun. And, eventually, to several conversations and an exchange of letters on the question of whether the Iraq war had been properly — or ever — declared. We said yes, through the authorization to use military force.

Cuomo said no. He reckoned that the authorization fell short of a war declaration of the kind that Congress has issued but five times. We haven’t abandoned the view that Mr. Bush had all the authority he needed, but we’ve come to the view that Cuomo’s point was full of wisdom. A declaration mightn’t be needed by the president, but the genius of the war declaration — “all of the resources of the country are hereby pledged,” one of them said — is the way it binds the Congress. We’ve never lost a war that we’ve declared.

That we’ve lost Mario Cuomo, in any event, is a sad day for New York, all the more so because there was a tragic element to Cuomo’s life — the sense that he, like such friends and rivals as, say, Mayor Koch and Cuomo’s own predecessor, Governor Carey, had been “marooned,” as one reader put it to us, in the Democratic Party of his youth and of his parents. Theirs was a faction from whom a once-great party was hijacked and marched off into the wilderness by the followers of Senator McGovern.

There will be plenty of time for an accounting of the ledger of the results and of Mario Cuomo’s own three terms as governor. Though history does not disclose her alternatives, we will wonder how things might have looked had Cuomo gone on to, say, the Supreme Court or had the Democratic Party taken a different turn than the one it did at the San Francisco, where he gave his most famous speech. Meantime we mourn the loss of a leader who was so alive to the world of ideas and to the study of history.