On October 29, leaders of the European Union will gather in Rome to sign the Union's new Constitutional Treaty. Praise for the document's uniqueness will undoubtedly be heard, and in this they won't be boasting, because the EU Constitution is unlike any other constitution ever written.
Most constitutions - including the American one - aspire to "freeze history," or to set up a lasting institutional order that will resist the winds of change. Indeed, a constitution is by its nature an attempt to "tame" history, to make it follow the laws of man rather than its own logic, including unwelcome contingencies and the whims of fate.
By contrast, the EU Constitution is written with the unspoken understanding that the institutions it is setting up are transitory, that they are far from optimal, and that it would be desirable to change them right now if political realities allowed it. But the realities of politics in today's Europe do not allow for the sort of document the signatories really wanted to draft, so the constitution that they did write is designed to establish a process of evolutionary change that will motivate further improvements along the way - improvement that will, it is hoped, one day obliterate the very arrangements today's EU Constitution is setting up.
Indeed, from the start, the architects of the Union's Constitutional Treaty never seriously expected that their draft would endure in the form in which they wrote it. Instead, they saw themselves as following Europe's long established pattern of step-by-step integration.