I have been watching Chancellors professionally for 25 years. During this time I've seen Budgets and Autumn Statements cheered and jeered by economists. But never have I known one to be greeted with as much incredulity as Osborne's effort on Wednesday. I've had numerous emails from City economists expressing the same sentiments as Stephanie Flanders and Rick - that his spending projections are "probably impossible" and in "la-la land".

This raises the question: what the hell is he playing at?

I think we can discount the possibility that he's laying a trap for the next Labour government - that when Labour tears up his projections they'll be accused of being soft on the deficit.

I don't believe this for two reasons. One is that politicians, being overconfident, rarely plan on being defeated. The other is that there can be no discredit in recognizing the impossible. A man cannot be blamed for cancelling plans to build a unicorn farm.

Another possibility is that he's setting a big hairy audacious goal - that he is, in fact, serious about cutting spending.

If he is, he's going about it in an astonishingly stupid manner. When James Collins coined the phrase BHAG he intended it to be a way of catalysing change. A BHAG is supposed to inspire people to think bigger, to ask how the goal can be achieved.

But this isn't happening. As I've said, Osborne hasn't prepared the ideological ground for a small state. And he's not making the organizational changes that small government requires. Quite the opposite. At least one government department - the Home Office - is acting as if we're in an era of ever-bigger government. He is ducking the challenge made by the IFS's Paul Johnson:

It is surely incumbent upon anyone set on taking the size of the state to its smallest in many generations to tell us what that means.How will these cuts be implemented? What will local government, the defence force, the transport system, look like in this world? Is this a fundamental reimagining of the role of the state?

If Osborne is serious, then his plans are mere cargo cult management, by which I mean this:

Step 1: Announce a target
Step 2: Magic!!!
Step 3: Target met

In this sense, what Nye Bevan said of Anthony Eden applies, mutatis mutandis, to Osborne: "if he is sincere in what he is saying, and he may be, then he is too stupid to be Chancellor."

There is, though, a third possibility, suggested by Stephanie. If you want to promise to return the Budget to surplus in the absence of strong economic growth whilst also holding out the hope of tax cuts, then as a matter of simple maths cuts of the size Osborne envisages are the only option.

But perhaps he doesn't intend to implement these cuts. Instead, he is merely promising to do so to appear tough and "in control of the public finances". And some political reporters are gullible enough to believe him. Maybe he's just following Machiavelli:

It is unnecessary for a prince to have all the good qualities...but it is very necessary to appear to have them.