Yesterday, visiting Edinburgh Women's Aid, Nicola Sturgeon said she believed firmly "that people who have concerns that their partner may have a history of domestic abuse should be able to find out".

Many would applaud the sentiment.

The First Minister is both a solicitor and a politician, however. She knows the differences, philosophical and practical, between one profession and the other. She knows when one must yield to the other and when, in conscience, it must not. In the hellish matter of abuse and forewarning, she has made her choice. Is she right?

Broadly, we believe so. Or, rather, we believe that reservations over aspects of what is called Clare's Law need to be tested thoroughly. The extension of a pilot scheme from Aberdeen and Ayrshire to the entire country, announced yesterday, should serve that end. If people are to be allowed information on the histories of previous partners, a range of issues need to be scrutinised.

What becomes of the presumption of innocence if potential partners have never been convicted? How should mischievous (and worse) inquiries be addressed? Does an early warning system, of sorts, take us closer to the causes of the problem? Above all, how does the law (it is no such thing) named for poor Clare Wood, dead in Salford in 2009, cohere with other approaches to domestic abuse?

None of this is to minimise the potential of a controlled disclosure scheme. If a single woman (almost always a woman) is kept safe, quibbling is beside the point. Domestic abuse, in all its varieties, has been society's miserable secret for too long. Police Scotland have been challenging that legacy by refusing to treat "domestics" as private affairs, and by recording incidents as evidence of actual or potential offences.

This is crucial. How can people ask for information about partners if no information has been recorded? How - the heart of the matter - can abusers be deterred? A change in policing habits can work wonders. It could also have the effect of surmounting legal obstacles where Clare's Law is concerned.

The test of any experiment is simple: does it work? Those who work in the field of abuse do not regard disclosure as a panacea. On the other hand, they do not reject the policy despite its limited application, or its sometimes problematic nature. If improvements are apparent in statistics - a result achieved by Police Scotland - judgments can be made.

The idea that suspicions can be offered as information and information treated as a kind of evidence will always be troubling. On the other hand, violent bullies have for too long hidden away in the home, taking refuge behind society's reluctance to intrude. With Police Scotland challenging that attitude, the harm caused to legal principle becomes tolerable.

With luck, we have begun finally to grasp the vileness and extent of domestic abuse; which is to say, predictably, that men have begun to understand. Any principle that fails to protect half the population cannot be sacrosanct.