At each stage of the unfolding catastrophe in Zimbabwe it has been tempting to believe that the situation could get no worse; and, if it did, this would result in President Mugabe's exit from power. Or, if not that, he would finally recognise that it was in his own interests to do no more harm to his country. On the Guardian website there are references to the "endgame" of Mugabe in 2002, 2003, 2004, and 2007.

Yet not only has Mugabe been unrelenting in his efforts to bring ruin to his country, but the prospect of his overthrow seems as distant as it ever was (if not more so). To understand why this is, one must first recognise Mugabe for what he is - or at least, has become - namely a tyrant. I use this description not as an epithet but as a way of seeing.

A tyrant, Aristotle wrote in Politics, "has no regard to any public interest, but only to his private ends." There is "no wickedness too great for him." Tyranny combines the vices of democracy and oligarchy. Its end, as with oligarchy, is wealth "for by wealth only can the tyrant maintain either his guard or his luxury." From democracy, meanwhile, tyrants have "borrowed the art of making war upon the notables and destroying them secretly or openly."

The methods with which Mugabe has entrenched his power since 2000 would have been familiar to the ancient world. The goals of the tyrant are simple: he must sow distrust among his subjects, he must take away their power, and he must humble them. Among the arts by which a tyrant preserves his rule are the following:

"[He] should lop off those who are too high; he must put to death men of spirit: he must not allow common meals, clubs, education and the like; he must be upon his guard against anything which is likely to inspire either courage or confidence amongst his subjects; he must prohibit literary assemblies or other meetings for discussion, and he must take every means to prevent people from knowing one another (for acquaintance begets mutual confidence)."

"A tyrant should also endeavour to know what each of his subjects says or does... for the fear of informers prevents people from speaking their minds, and if they do, they are more easily found out. Another art of the tyrant is to sow quarrels among the citizens...."

Mugabe has been very successful in applying these prescriptions. The white commercial farmers (the ‘notables') have been destroyed, and their urban equivalents are soon to be as well. Most ‘men of spirit' have been driven into exile. The judiciary has been suborned and the citizens can have no confidence that their rights will be protected in the courts. The Daily News, the main ‘literary assembly', was shut down long ago. CIO informers are everywhere and seem to know everything.

Through violence, intimidation, and vote-rigging, the Zimbabwean people have been deprived of their power to vote his regime from office at the ballot box. And after three stolen elections they seem to have lost courage as well. As Aristotle observed, if the people "are always kept under, they will learn to be humble." The opposition Movement for Democratic Change quarrelled and is now divided.

Yet surely economic collapse will precipitate revolution? This is not necessarily so. Aristotle writes that to preserve his power the tyrant "should impoverish his subjects; he thus provides money for the support of his guards, and the people, having to keep hard at work, are prevented from conspiring."

There is a terrible logic to these actions. The tyrant humiliates his subjects for he knows that "a mean-spirited man will not conspire against anybody"; he sows distrust among them for he cannot be overthrown "until men begin to have confidence in one another"; and, he tries to ensure that they are "incapable of action, for no one attempts what is impossible, and they will not attempt to overthrow a tyranny, if they are powerless."

After eight years of repression the opposition forces in Zimbabwe seem too weak to effect a change in government. Tyrants can also be brought down through internal divisions within the ruling clique. But, so far, Mugabe has proved more than capable of dealing with those in ZANU-PF who wish to displace him. It is characteristic of a tyrant, Aristotle wrote, "to distrust his friends, because he knows that all men want to overthrow him, and they above all have the power."

Since the worse things are for Zimbabwe, the better they are for Mugabe, the crisis in that country is not going to resolve itself. The initiative for change is probably going to have to come from without. Crucially, South Africa has to reverse its existing policy of public (and private) support for ZANU-PF. You only need to read the government press in Zimbabwe to see how this is used by the regime to undermine the courage and confidence of the populace there.

For example, on March 30, after his return from the SADC summit, Mugabe claimed that Mbeki had told the meeting: "If we condemned Zimbabwe, the same methods would be used by the West against us. The view of these white people is that all leaders of liberation movement parties must be removed and replaced by puppets."

In May, after SADC's mediation process was launched the ZANU-PF cabinet minister, Emmerson Mnangagwa, taunted opposition MPs in parliament by telling them that Mbeki was requiring the MDC both to "accept and recognise that President Robert Mugabe is the president of Zimbabwe and he won the [stolen] 2002 elections" and to "denounce violence." Mbeki had, Mnangagwa continued, set "no conditions" on ZANU-PF's participation.

Earlier this month the Zimbabwe Herald reported that Mugabe had told a public meeting that on the last official visit to South Africa by the then British Prime Minister, Tony Blair, Mbeki had told Blair "to back off from meddling in the affairs of Zimbabwe as SADC was handling the matter."

The South African government has, for whatever reason, chosen not to contradict these reports. In any event, whether they are true or not they serve their intended purpose. The message the Zimbabweans are hearing is this: Within SADC and the African Union you are morally isolated and alone. South Africa is on our side.