The assumption is of ten made that you can have equity or efficiency, a fair society or a profitable economy - but not the two together.
One of the biggest challenges facing Labour and Democratic Left as they join forces today is to prove that this is not so. Equity and efficiency are not mutually exclusive.
This has to be at the core of the left's approach at a time of extraordinary prosperity, deepening division and increasing uncertainty about the direction of Irish life.
First however, it means showing that in spite of the abuses of some politicians and the woeful inefficiency of others, politics is not a dirty word.
Equity and efficiency never were mutually exclusive, although they've long been confused with patronage, whether those patronised were businesslike cronies at one end of the scale or impoverished clients at the other.
The political roots of this confusion were in the 2 1/2 party system, where it was easy to see who was who: the fellows with the caps were the Labour crowd. The men they saluted belonged to Fianna Fail and Fine Gael.
Labour knew its place and its obligation to wait. (In the national interest.) Fine Gael would share power with it when the time was right, in Fine Gael-led coalitions.
Fianna Fail would look after its constituents as assiduously as if they were its own: it was a classless society and this was the natural order of things.
Now, there are other myths just as clearly designed to throw the public off the scent of power, privilege, influence and corruption. The message sounds different. The line of argument is the same.
It used to be said that Labour could safely leave the serious stuff to Fianna Fail and Fine Gael. Now, the claim is that nothing can be changed, certainly not by politics, definitely not by the left.
Two criticisms are heard again and again. One is that all parties have moved to the centre - so there's no real difference between them. No con flict. No contest of ideas. No choice for the electorate. No alternative government.
The other is that all the real decisions are made either by the European Union or by big business, as often as not in secret, with a minimum of discussion and little or no reference to the electorate.
The European Union is a political as well as an economic entity. All but two of its members are governed by leftwing or left-led administrations. The most powerful group in the parliament are social democrats.
The EU leaders now gathered in Vienna are meeting under the presidency of a new German government of social democrats and Greens.
The issues under discussion in the EU - the budget, structural funds, regionalisation and, in due course, the harmonisation of taxes - are of particular significance in Ireland.
We are no longer a poor state dependent on richer neighbours. It's becoming clearer by the week that a new approach to EU affairs is essential; so are new allies and a keener sense of what's happening in the wider world.
Already, there is the beginning of a debate about contrasting ways of tackling social and economic affairs which sets the European approach against the American.
It's a debate which will determine the direction of this society in the next 10 to 20 years, and it's showing up serious ideological differences.
On one side are those who favour the market alone as an arbiter of how our needs are met, essentially how our society is to be organised. Call it the Ryanair way. On the other are those who believe the public interest is best served by partnership and regulation, by what their opponents gleefully deride as the nanny state.
The debate isn't confined to the political arena. Indeed, few politicians have chosen to identify themselves with the American way, and some in the catch-all parties are distinctly uneasy about taking sides. Some complain that the left assumes it has a monopoly of morality, as if morality was a section of the political market to be cornered by the first comer.
The truth is that, on the increasingly important issue of standards in public life, the left is best placed to lead the way. At present, by all accounts, it's strapped for cash.
Paradoxically, that gives it an advantage over parties which have deeper pockets but real or presumed obligations to their sponsors.
Besides, the left has a much more impressive record than its opponents or their campfollowers in the media.
Labour and DL, with such honourable members of other parties as Des O'Malley, have consistently demanded openness and accountability.
Labour promoted the laws on freedom of information and ethics in office, for which Eithne Fitzgerald was roundly criticised by the conservatives of FF and FG before winning their grudging support. Her efforts were derided by some commentators and ignored or misunderstood by others, for whom politics is a dirty word.
The left demands the protection and promotion of the public interest; the right complains about what its industrial and media allies call the nanny state. The left insists on openness and accountability; the right argues that in the real world - a place the unemployed, the poorly paid and the handicapped clearly know nothing about - life doesn't work like that.
There is a suggestion that not only are equity and efficiency mutually exclusive, the efficient by the very nature of their enterprise are special cases - and entitled to cut corners.
But cutting corners, as we've seen, leads to some riding roughshod over the planning laws, company laws, financial regulations and other controls designed to ensure that in this Republic every citizen is bound by the same code.
The left more consistently than any other group hammers home a message of political responsibility: when ministers refuse to answer questions in the Dail or politicians appear to use their positions for personal gain, they must be held to account.
The left is not alone in its insistence, but it is the most consistent. It has made political mistakes and paid for them. It has shed most if not all of its foolish rhetoric.
The most telling events of the week, however, were the revelations by Mr Justice Flood and Mr Justice Moriarty of failures to co-operate with tribunals established by the Oireachtas to investigate issues implicating politics and business.
The new party can do no better than insist on the primacy of politics.