HOW long should a constitution be? For some, the answer to the question is “the shorter the better”. There is a view, quite often expressed in Scotland, that a new constitution should be just a page or two in length.

Certainly, iconic, world-changing, identity-defining documents can be quite short. The US Declaration of Independence is about 1350 words. The Declaration of Arbroath (in English translation) about the same. The Sermon on the Mount, in the King James version, comes out at about 2500 words.

Such a short constitution would set out general principles and overarching values, while leaving all the institutional details to be worked out in ordinary legislation. It would be designed to be accessible and memorable – something that can be written on the doorposts of our houses and on our gates, so to speak.

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Angus Reid’s Call for a Constitution took this to its logical conclusion, condensing essential principles into fewer than one hundred words, which he then painted on walls and windows across Scotland.

Long constitutions, in contrast, are seen as exercises in obscure legalese: confusing that which should be clear; obfuscating that which should be common knowledge. In other words, they are presented as just another con by which “they” keep “us” far from power.

It is necessary, however, to push back against the idea of a very short constitution. Constitutions do express values, principles and ethical foundations, but they do a lot more besides. They define and protect rights, and they establish and regulate public institutions. These things take a fair few words to do well and to do right.

There is something of a paradox here: long, detailed, specific documents are often clearer, and less subject to legal wrangling, than short documents that deal only in generalities.

This can be seen from a comparison between two neighbouring countries, both with late 20th century constitutions: Liberia and Sierra Leone.

The Constitution of Liberia devotes just 45 words to the establishment of the Civil Service Commission, Elections Commission and General Auditing Commission; it states that these are “autonomous public commissions” and gives the legislature authority to “enact laws for the governance of these commissions”. In practice, this means that it is up to the legislature to determine the appointment, tenure, independence, powers and functions of these commissions. They can be altered to suit the interests of the incumbent legislative majority. The courts, if called upon to determine the constitutionality of such legislation, have very little to constrain them, except for deference to the legislature and the imprecise notion that these commission are to be – in some general, unspecified way – “autonomous”.

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The Constitution of Sierra Leone, in contrast, devotes nearly 3000 words to the equivalent institutions. This constitutional specificity gives these institutions additional protection; their appointment, tenure, independence and powers and functions are embedded in the constitution and not, therefore, subject to easy manipulation by the incumbent majority. It also reduces the scope for judicial interpretation. The more precise and detailed the text of the constitution is, the less lawyers can argue over.

The average length for constitutions in the European Union is around 15,000 words. As a general rule, new constitutions are longer than old ones, federal constitutions are longer than unitary ones, and British-derived constitutions are longer than those in the European tradition – typically between about 25,000 and 50,000 words.

This last difference, which explains why the Constitution of Malta is the longest in the European Union and that of India is the longest in the world, derives from different approaches to legal drafting and statutory (and therefore constitutional) interpretation.

The great constitution-maker Sir Ivor Jennings, in The Approach to Self Government (1956), described his experience of working with a French-trained colleague to draft a new constitution for an undisclosed African nation.

For the French jurist, it was sufficient for the constitution to state general principles “the legislature shall be elected by universal adult suffrage”; the details could be worked out by legislation, and that legislation would be interpreted and applied in accordance with those general principles.

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For Jennings, this was nonsense. Such high-sounding generalities would only cause a legal quagmire. He insisted on a more specific approach: the constitution should define, in detail, the qualifications for the franchise, and should list any disqualifications in detail too. That, only that, would give legal certainty and limit the scope for jiggery-pokery.

Calls for a short statement of values and principles are understandable. There is a place for the memorable, the rhetorical, even the poetical, in constitutions. That place is the preamble. The preamble invokes the spirit that animates the letter of the constitution. It can be something that every secondary school child is capable of learning by heart, as a part of their civics education.

Behind this front, however, the real work of the constitution must be done – and it is necessarily a prosaic rather than poetic exercise.

Roger Mullin is next week’s guest on the TNT show, at 7pm on Wednesday.