F.A. Hayek on The Constitution:
When Montesquieu and the framers of the American Constitution articulated the conception of a limiting constitution that had grown up in England, they set a pattern which liberal constitutionalism has followed ever since. Their chief aim was to provide institutional safeguards of individual freedom; and the device in which they placed their faith was the separation of powers. In the form in which we know this division of power between the legislature, the judiciary, and the administration, it has not achieved what it was meant to achieve. Governments everywhere have obtained by constitutional means powers which those men had meant to deny them. The first attempt to secure individual liberty by constitutions has evidently failed.
Constitutionalism means limited government. But the interpretation given to the traditional formulae of constitutionalism has made it possible to reconcile these with a conception of democracy according to which this is a form of government where the will of the majority on any particular matter is unlimited. As a result it has already been seriously suggested that constitutions are an antiquated survival which have no place in the modern conception of government. And, indeed, what function is served by a constitution which makes omnipotent government possible? Is its function to be merely that governments work smoothly and efficiently, whatever their aims?
In these circumstances it seems important to ask what those founders of liberal constitutionalism would do today if, pursuing the aims they did, they could command all the experience we have gained in the meantime. There is much we ought to have learned from the history of the last two hundred years that those men with all their wisdom could not have known. To me their aims seem to be as valid as ever. But as their means have proved inadequate, new institutional invention is needed.
Law, Legislation and Liberty: A new statement of the liberal principles of justice and political economy F.A. Hayek 1-2 Routledge. Kindle Edition.