Travelling through the United States, New Zealand, Australia and South Africa during September, with a view to lecturing in the last three, I could not help being struck by the differences between the political systems of these four countries, writes Garret FitzGerald.
The US and South Africa have presidential systems, while Australia and New Zealand, like Ireland, have inherited parliamentary systems from the period of British rule. And I am inclined to think that we may underestimate the significance of the differences between these two rival forms of democracy.
It is not surprising that in the 18th century before (or in the case of Britain in the early stages of) the emergence of parliamentary democracy, the US chose a monarchical form of government - albeit an elective monarchy with checks and balances through elected bodies.
Because the American Revolution occurred before ministers in monarchical Europe became responsible to a majority in an elected parliament rather than to the monarch who appointed them, the US had no democratic parliamentary model upon which to base its new political system. Moreover, the new federation needed a focus of unity that its founders felt only an executive president could provide.
As for France, the failure of the parliamentary system in 1958 to cope with stresses deriving from the colonisation of Algeria provided de Gaulle, as incoming prime minister, with the necessary popular support for a peaceful revolution that abolished the parliamentary Fourth Republic, and installed the general as executive head of state in a presidential system.
Today's other two major presidential systems, those of Russia and South Africa, seem to reflect from a perceived need for these two states, emerging from peaceful revolutions, to have strong governments capable of securing stability.
In most of Europe, however, the hereditary monarchs survived until 1918 by accepting a gradual process through which ministers they appointed from the 17th century onwards to help them run the increasingly complex affairs of their kingdoms gradually became increasingly responsible to elected parliaments.
Control of taxation, and later the monitoring of expenditure by elected parliaments, had gradually given these elected bodies the necessary leverage to ensure that only a ministry acceptable to them could survive, thus curbing much of the monarch's power; although in many countries foreign and security policy had remained under monarchical control or influence.
By tradition heads of state, whether hereditary monarchs or elected presidents, provide a focus for national unity, and respect and deference accorded to them contributes to this process.
In a number of European countries hereditary monarchs who have adjusted to this reduced role, and who respect the public preference for a more classless society, still fulfil this role very successfully, in some cases better than superannuated politicians elected by a parliament to presidential office.
(Ireland is unusual in having a non-executive president chosen by the electorate rather than by parliament).
It seems to me, however, that a problem can arise in a political system where the elected president has an executive role and by virtue of being head of state is sheltered, sometimes to a high degree, from the questioning and criticism to which prime ministers in parliamentary systems are subjected, both in parliament and by the media.
The contrast between the ways in which these two political systems work has recently been dramatically highlighted by the very different experiences of President Bush and Prime Minister Blair in relation to their Iraq adventure.
From the outset Blair was under intense pressure from both Liberal Democrats and his own backbenchers in parliament, as well as from many of the media, all of whom vigorously question his actions in a manner from which Bush was largely exempt, by virtue of his position as head of state, and also commander-in-chief.
Bush did not have to face questioning in Congress, a process to which Blair was subjected every week when parliament was in session. And, apart from one interview by an RTÉ journalist (which served to highlight the extent to which US journalists are unwilling to cross-question their head of state), Bush was never put under pressure on television and was treated with kid gloves by journalists at press conferences.
Now, as someone who as taoiseach has been through this whole process, I can testify to the fact that having to answer for all one's actions both to parliament and to a critical and uninhibited press is a very effective check on the exercise of political power.
Together with our constitutional provisions protecting human rights, which are invigilated by courts that do not hesitate to strike down even unintended, and sometimes quite technical and minor, breaches of such rights, this public questioning process provides strong protection against abuse of power by any government.
As a citizen I find this a source of comfort - and of pride. I would not feel anything like as comfortable in a presidential system, even in one where elected representatives have the power to investigate the actions of the executive after the event and, in the extreme case, to impeach the president.
The US president's power to appoint Supreme Court judges is also dangerous in a country where deep ideological divisions politicise the court in a way that does not happen in our more pragmatic political environment where, despite a party political element in the appointment process, the strong ethic of the Irish Bar ensures against political bias in court decisions.
In France the president seems to be immune from investigation, even on corruption issues, so long as he is in office. In Russia, with a weak parliament, there are few restraints on President Putin's exercise of executive power, and he has recently been further restricting the media, most of which are already under his effective control.
He has also used the recent Chechen atrocity as an excuse to introduce political reforms that will strengthen his power, some of them quite irrelevant to the security issue.
Of course, abuses of power can occur in parliamentary as well as presidential systems where the ruling parties are dominated by a strong leader - as in Italy where the Prime Minister, Mr Silvio Berlusconi, has both secured for himself immunity from prosecution for alleged corruption and has also used his position to strengthen his personal control of many of the media.
Nevertheless I am of the view that the presidential system of government is more prone to abuse and offers much less protection for the citizen.