A nation's parliament should reflect the people it represents.
There should be as many women as men in the chamber, and the balance of ethnic, religious, social and economic backgrounds should be broadly similar to the country at large. Every progressive, modern parliament should aim to meet this standard.
Sadly, as figures published in The Herald today demonstrate, Scotland's parliament is failing to pass the test in one critical respect: education. A breakdown of the educational records of MSPs shows that 17% were educated in independent schools compared to only 4% of the population at large. It is a striking difference, particularly as educational background is one of the most important drivers of social mobility.
The figures vary for each of the parties. Conservatives are much more likely to be independently educated, although the proportions are relatively high too for the Labour Party, with 13% of its MSPs having gone to a private school - almost 10% higher than the rate for the population generally. The figure in the SNP is another 2% higher than that at 15% and for Liberal Democrats it is zero, although the party only has five MSPs.
There is some comfort to be had by comparing the situation to Westminster. There, 34% of its members were educated privately and the influence of Eton in particular is famously pervasive. Even the Cabinet minister Michael Gove described the number of former Eton pupils at the top of government as ridiculous, although Mr Gove himself was also privately educated in Scotland so some might think, coming from him, the criticism is a bit rich.
What today's figures in The Herald show is that at least Holyrood is more balanced than Westminster - all the Scottish party leaders were educated at comprehensives, for instance. But the influence of private schools in Scotland is still strong and anyone who cares about social mobility should be uncomfortable that many more MSPs go to private school than the general population.
Part of the problem is that the typical politician has changed in the past 50 years, with non-graduates increasingly pushed out in favour of graduates, which gives private pupils an in-built advantage - more than 80% of private pupils will go to university while in some state schools it is less than 25%.
However, as Professor Michael Keating of the Scottish Centre for Constitutional Change points out, the prevalence of private education in parliament is to be found in other areas such as law and business. In other words, the imbalance at Holyrood reflects the inequality of society as a whole.
If Holyrood is to change, it is this wider inequality that has to be tackled and it must be done on several fronts: child poverty must be reduced, the gap between schools must be narrowed, access to university and careers must be widened. When problems such as those are taken on, and society as a whole is made fairer, perhaps then the Scottish parliament will become a fairer and more equal place too.