In breaking news overnight, the Irish Greens have reached an agreement with the ruling Fianna Fail party, under which the Greens will join a coalition government.

Readers might remember that last month’s Irish election left the outgoing government ahead of its rivals, the Fine Gael-Labour coalition, but still short of a majority. The Greens’ six MPs, together with some sympathetic independents, will remedy that, ensuring Bertie Ahern’s re-election as prime minister when parliament meets on Thursday.

That’s good news for stable government in Ireland, but it’s more interesting as another step in the European Greens’ journey into the political mainstream.

The Greens have come a long way since their emergence in Germany in the 1980s. Originally regarded as fringe-dwellers, they have gradually become candidates for participation in government. The Finnish Greens joined a coalition government with the social democrats in 1995; the German party followed suit in 1998.

But to be really taken seriously the Greens needed to be able to manoeuvre between left and right. In 2003, the Austrian Greens formed a coalition with the centre-right in the province of Upper Austria, and later had serious talks about doing so at the national level, as did their German counterparts in 2005. Now the Irish Greens have made common cause with Fianna Fail – which, murky though its ideology might be, has to now be regarded as more right than left.

This is how coalition politics works. When parties are represented roughly in proportion to their actual support, they can deal with one another to get the best outcome for their followers and their policy goals. If they give away too much, or support a government that their voters object to, they know they will pay an electoral price.

Our electoral system, however, denies minor parties any participation in forming governments, so the Australian Greens (with the exception of Tasmania) have never had to deal with the realities of coalitions. Shut out from responsibility, they are free to indulge in doctrinal purity. (Family First looks like going much the same way.)

So those who argue that we shouldn’t give more of a say to minor parties because they’re unrealistic extremists have it the wrong way around: the way to turn extremists into responsible citizens is to bring them within the tent. We could all learn a thing or two from the Europeans.