Was she the greatest post-war leader the world has seen, or was she greater? The "post-war" qualification in obituaries this week was to take Churchill out of the equation. I'd like to put him in.
Margaret Thatcher, like all of her generation, drew inspiration from Winston Churchill. She grew up in World War II and recalled in her memoirs how his radio broadcasts left her with the conviction that "given great leadership there was almost nothing the British people could not do".
But war is an advantage to leadership. A threat on the scale faced by Churchill's Britain unites a country, suspends party politics, employs practically everyone and subordinates all the usual dilemmas of government to a single overwhelming task.
Unless the Prime Minister is palpably weak he can hardly fail to be great. A statue of Churchill at Westminster shares a lobby with David Lloyd-George, who'd be no more memorable than any of Britain's prime ministers of the early 20th century had he not been in office through the first war.
Two other 20th century figures stand in that lobby. One is Clement Attlee, the scarcely remembered Labour Prime Minister who, for all Churchill's wartime greatness, defeated him at the election of 1945.
The other is Margaret Thatcher.
To find statesmen of the century whose global influence was comparable to hers, you have to go presidents of the United States. It was, after all, the American century.
Woodrow Wilson and Franklin Roosevelt were also wartime leaders but their main achievements were post-war in Wilson's case (organised international co-operation) and pre-war for Roosevelt. His "New Deal" made Keynesian economics the world's governing orthodoxy for the next 40 years. Keynes in fact was undoubtedly the century's most influential figure.
But if we are talking about politicians - the people who put good thinking into action and submit themselves regularly to the judgment of free voters - then I think Mrs Thatcher takes the prize.
She led a late-century return to free markets, floating currencies, low inflation and balanced budgets.
Post-war governments before hers had carried out only one side of Keynes' prescription, running deficits to finance welfare states with collective wage bargaining, industry protection and economic controls that worked well enough for 25-30 years.
Then, in the 1970s, they were no longer working. Wages and prices were constantly rising and people were grumpy. Too many were now unemployed, depending on benefits, and those that had work didn't care much about it.
The Britain I first saw in the late 1970s was a deeply depressed society. People had gone beyond embitterment to adopt a cynical, amused resignation to their condition. Service was sullen, public amenities were grimy and graffiti-ed. Old industries survived on public subsidies and trade union power.
The unions had brought down one government and their bosses were negotiating the nation's economic management with another.
Soon after I arrived and got a job I had to go on strike. It was to last for three months, the now famous "winter of discontent". I felt like a pawn in somebody's pointless game.
When the 1979 election was called, serious newspapers debated whether the Tory leader was "electable", which meant, "could she work with the unions". I had my doubts for another reason: she was a starchy matron who could not be less like the British I'd met.
She talked about Britain in a way that was completely out of step with the cynicism of the age. When she went on about putting the "great" back into its name, you could feel the place squirm.
Nobody had a good word for Mrs Thatcher, probably because they didn't want to seem old fashioned like her, but in the secrecy of the booths they voted for her.
Even now they struggle to acknowledge her stature. I'm not talking about the tasteless, graceless left who openly celebrated her death this week. Serious obituaries blamed her for the global financial crisis and the consequent recession, now in its fifth year.
I wonder what she would have said about the loose monetary policies of the US Federal Reserve after 2001 and what she would have done after the crisis. I suspect she would have forbidden the debasement of currencies called "monetary easing".
Britain might have had a shorter and sharper recession and now might be three years into a recovery that business could believe. Firms would be expanding, not sitting on the cash of monetary easing.
It speaks volumes for Mrs Thatcher that Labour MPs in the House of Commons this week could not offer her an unequivocal tribute. Her principles and policies remain too powerfully alive.
Churchill, Roosevelt, Wilson, Kennedy, Gorbachev were all great in their way. But when I ask myself who was the most clear-headed, courageous and effective leader of our time, it was that woman.