It is incumbent on people who advance controversial claims or argue against mainstream views to prove their case. They must substantiate their ideas to the satisfaction of experts in the field.
"Moon Man" Ken Ring has failed totally to convince the scientific community that his method for predicting earthquakes has merit. But, unfortunately, he appears to have persuaded many people that another large quake will strike Christchurch tomorrow.
Quite why they have been taken in by a view devoid of scientific underpinning is something of a mystery. Perhaps it is something to do with the fact that earthquakes, the cause of such death and destruction, cannot be predicted.
It is only natural to seek certainty, particularly in fraught times. There is, therefore, comfort of sorts in being advised when a quake will strike. But there is also heightened alarm. When people say they plan to flee Christchurch on the predicted day of danger, it is time for the scientific community to speak up.
Commendably, that happened this week. Sir Peter Gluckman, the Prime Minister's chief science adviser, strongly criticised Mr Ring. Vulnerable regions could be identified and the likely magnitude of a quake could be predicted, but not the precise locality, depth or timing, he said.
There can be no certainty.
On another tack, Government minister Nick Smith said he would lunch in one of Christchurch's highest and oldest stone buildings tomorrow. He has a doctorate in geotechnical engineering. If men with such scientific credentials are not alarmed, nor should Cantabrians be.