If I were a megalomaniac I might think that Benjamin Netanyahu has resigned just to spite me. Only last Friday, I published a column in The Jerusalem Post in which I wrote:

“There are indeed two reasons why we should want Bibi to remain Israel’s finance minister for as long as possible. One is that this will keep him from being prime minister, a post for which he still seems eminently unsuited. The other is that he has been doing a superb job where he is.”

“Drat him!” the megalomaniac columnist can imagine Mr. Netanyahu saying. “I’ll show him who’s suited for what!”

Actually, no one seems to know exactly when Bibi made up his mind. Was it already settled months ago, the idea being (as he claimed at a press conference given hours after resigning) to first see to completion the economic reforms his ministry had been working on, or was it a spur-of-the-moment decision determined by various considerations – chief among them (as he claimed at the same press conference) his growing worry about the course that Prime Minister Sharon’s disengagement-from-Gaza plan was taking and about its lack of safeguards for Israel’s security?

It’s hard to know with Bibi, especially when he says contradictory things, because he has an unusual talent for making you believe whatever he says. Although he has often been called the Great Communicator of Israeli politics, one wonders whether politics don’t cramp his theatrical gifts. If Ronald Reagan was a mediocre actor who became a great politician, Benjamin Netanyahu sometimes strikes one as a mediocre politician who could have been a great actor.

His post-resignation press conference statement was a marvelous example of this. At first, as I watched it on TV, I judged it to be a failure. It seemed impromptu, too emotional, poorly thought out. It started in the middle, and went from there to the beginning, and couldn’t seem to get to the end. What was the man trying to say?

But after a while, I saw that I’d missed the point. The man was being, as usual, media-brilliant; what he was saying was exactly that. What was impromptu and emotional, he was conveying, was his decision itself; his delivery was merely the outward sign of it.

Here was a man, this delivery declared, who had been through weeks and months of agonizing inner debate – who had put aside all thought of personal loss-and-gain in order to concentrate on the problems of the nation – who was torn between his duty to the economy (who else could manage it as well as himself?) and his fear of disengagement’s perils (who else could warn of them as effectively as himself?) – who now, overwhelmed by his sense of responsibility, had realized at last that he could not remain in his position one more day. Who could expect such a presentation of inner turmoil to be perfectly smooth or coherent?

There are indeed rare politicians – Bill Clinton is another – who are so persuasive in their displays of sincerity that we want to trust them even when we know we shouldn’t. Perhaps they are so convincing to others because they have first convinced themselves; like method actors, they work themselves so deeply into their roles that their roles are what they become. What, after all, is the difference between being sincere and feeling sincere? If you feel it, doesn’t that mean you are it?

Well, no, to tell the truth it doesn’t. It’s only onstage that well-acted sincerity and real sincerity are functionally the same thing. Offstage they are distinguished by the fact that real sincerity is consistent.

And consistent is what Benjamin Netanyahu has never been – certainly not when it comes to disengagement. He was inconsistent when he said at his press conference that (a) he had known from the start that unilateral disengagement from Gaza would be a disaster because giving the Palestinians something for nothing encouraged terror and (b) he had only realized in recent weeks that it would be a disaster because Ariel Sharon’s turning over of the Gaza-Egyptian border to the supervision of the Egyptian army, and his agreement to the construction of a Palestinian deep-water port in Gaza, were grave dangers to Israel.

He was inconsistent when he declared in the past that Israel’s economy could and must be made to thrive even when its security situation was grim, and when he declared at his press conference that he could no longer continue as the country’s economic chief because after disengagement its security situation would be grim.

He was inconsistent in his attitude toward disengagement all along – first refusing to take a clear stand on it when it was put to a Likud referendum, then voting for it at cabinet sessions while saying privately that he opposed it then playing hooky from voting and now telling us that he was against it from the start.

Consistency, of course, is not a virtue commonly associated with politics. Politics is the art of sailing by the wind, and when the wind changes so do politicians. But as long as our political leaders understand what they are doing – as long, that is, as their private cynicism keeps them honest even while they are publicly lying – they are not necessarily unfit for high office. Although we cannot trust their promises, we still may trust their judgment.

The problem with politicians like Benjamin Netanyahu is that we cannot count on their cynicism to keep their judgment unclouded. They are too caught up in acting sincere to distinguish their passing moods from the truth. They’re not types to be running a country.

Mr. Halkin is a contributing editor of The New York Sun.