Even as evidence piles up all around, indicating that some of our old, fondly held beliefs may need to be rethought, we continue doing exactly what we've done before.

It's so safe precisely because it's exactly the way society works. A couple of people become convinced that a particular model explains the world. They reckon they can see what's coming next. Their certainty encourages others to believe; textbooks are written, and general interpretations - which may or may not be true - shift from mere explanations to conventional wisdom.

We all know the story of Galileo Galilei. In the early 1600s he confirmed earlier findings proving the Earth was not at the centre of the universe and in fact revolved around the sun. In 1632 the Roman Catholic church tried him for heresy, placed him under house arrest and, perhaps more importantly, attempted to prohibit any further discussion of the topic.

Galileo committed two transgressions. The first was challenging accepted wisdom about the way the universe worked; that was a problem, but not a crime. The real issue for the establishment was that he ridiculed the church and threw into doubt all the traditional interpretations. He encouraged people to question their fundamental belief as to who discovered "knowledge", and what was true. This posed a far greater threat to the people governing society than the other, comparatively minor issue of whether the Earth spins round the sun.

Similarly, today, since the borders have closed, two facts have become evident. The first is that immigration has collapsed, and the second is (directly contradicting all predictions) that overall employment has risen. Evidence is still coming in, and it's too early to absolutely insist these changes are directly correlated. It does, however, challenge one of the most fundamental assumptions on which our politics is based: the need for a "big Australia".

Immigration has provided incalculable and massive benefits to the country, not least the welcome injection of cultural diversity. Without Mediterranean immigrants we'd have no idea how to make coffee, and if our food hadn't benefited from the injection of Asian cuisine we'd still be eating beef and three veg. There's equally no doubt about the huge advantages that come with importing educated, hard workers who've brought knowledge and money from overseas, and this column should in no way be seen as an argument for a monocultural, closed nation.

What is worth questioning, though, is if we actually need to return to the previous, huge level of immigration. This is a fragile land, and the environmental argument for a reduced program is well understood. This is now being joined by an understanding that every new migrant also comes with a cost.

Maybe if we really want to reduce unemployment we need to rethink our immigration program.