The widely held view that President Jacob Zuma is out of his depth rattled him enough to cause him to protest at a recent National Union of Mineworkers function: "I know what I am doing ... I am not here by mistake."

Nothing in his cabinet reshuffle a few days later added credence to his confidence. Zuma has made 27 changes to his executive since he was elected in 2009. This includes deputy ministers who are not technically members of the cabinet - they attend by invitation and would not have a vote if a vote were called.

It is hard to imagine how Zuma's team is ever supposed to settle down to the job of making South Africa work when he continues to use cabinet appointments to reward or to punish colleagues, not for their work but for their politics.

He has sacked or moved 14 full ministers in his three cabinet shuffles. Only half of his original executive team, including deputies, still have the job he gave them in 2009. Four current ministers - Trevor Manuel, Jeff Radebe, Derek Hanekom and Nkosazana Dlamini-Zuma - were in Nelson Mandela's first 30-member cabinet.

Only Manuel and Dlamini-Zuma have served in the cabinet without a break since then. Manuel, Dlamini-Zuma and Zuma himself are the only members of President Thabo Mbeki's 1999 cabinet who are in office today. If Zuma succeeds in palming his former wife off on the African Union, as he is trying very hard to do, we can expect at least one more shuffle before the end of his term in 2014.

In sharp contrast with Mbeki, whose few mid-term changes mainly were forced by death or illness, Zuma obviously does not feel his frequent changes reflect badly on his judgment. The exception to Mbeki's often excessive loyalty to his own judgment was, of course, his dramatic dismissal of Zuma as deputy president in June 2005, after he had been named in the conviction of Schabir Shaik for fraud and corruption.

But if Mbeki overdid the continuity thing by keeping people like Stella Sigcau in office for far too long, Zuma clearly does not see that people doing such a tough job need time to learn and then to implement if their departments are to succeed.

Perhaps he bases his decisions on his own experience of the minimal depth he has felt it necessary to bring to the job of being president. The academic Steven Friedman was the first analyst I heard to make the point that, though cabinet shuffles usually have a point, Zuma's rearrangement of the deck chairs on his ship appeared to have none. Of the nine changes he announced last week, all Zuma absolutely had to do was replace Roy Padayachie, who died in office while on a trip to Ethiopia.

The only new minister to join the team was KwaZulu-Natal veteran Ben Martens, who could have taken Padayachie's job as minister of public service and administration.

Instead of doing the obvious, however, Zuma moved Lindiwe Sisulu from defence to public service, her third cabinet job, and replaced her with the serially incompetent Nosiviwe Mapisa-Nqakula. Mapisa-Nqakula destroyed the department of Home Affairs between 2004 and 2009, causing Britain to withdraw our visa waiver and the world to view our passports with disdain, before she was transferred to wreak the same havoc in the prison service.

Now she is being sent to do the same to the defence force.

The leadership of the transport department has been shattered with the simultaneous removal of Sibusiso Ndebele and his deputy, Jeremy Cronin. Ndebele takes over prisons and Cronin is the new second fiddle at public works.

There is no analysis of the performance of Zuma's largely disappointing team that would explain the range of changes he has made.

The hidden meaning that Friedman referred to can only have to do with Zuma's desperate struggle to remain in office - as president of the ANC in December and of the country in April 2014. And it is more apparent than ever following this shuffle that he cares not a fig for the job of government but only for the internal politics of the ANC and his continued role in it.

Perhaps Sisulu, whom I have previously compared to Marie Antoinette, will prove to be more of a Maggie Thatcher and succeed in the current wage negotiations in breaking the excessive power of the unions. If she does, however, it probably will be after a long and brutal showdown and at great cost to our economic stability.

If her record of confrontation with the military unions is anything to go by, Sisulu prefers the blunderbuss to a fencer's foil.

If Ndebele messed up on e-tolling, he is unlikely to be able to untangle the history of corrupt procurement at Correctional Services.

At least he had racked up some experience of transport so probably should have been left to continue, with the benefit of hindsight.

One should perhaps hope Zuma is indeed dead wrong when he says he knows what he is doing because if he does know and he keeps on doing it, there is something terribly wrong with his motives. As for his assurance that he is not where he is "by mistake", his primary backer in 2007, the ANC Youth League, has acknowledged that it sees its support for him as a dreadful mistake.

Many would agree with it on this, if on nothing else. Every leader of a democracy takes reward for political loyalty into account in the allocation of cabinet jobs, but the good ones have good and clever friends to choose from and do so wisely.