The French philosopher Jean-Paul Sartre once said of his nation: "We were never so free as during the German occupation." It sounds paradoxical, outrageous, even, but I have been reminded of the truth it contains by the current debate about selling booze.

Scotland is in the process of implementing its first major licensing law reforms for 30 years, and the new regime has an indisputably paternalistic nature. It is explicitly designed to help cut alcohol-related crime, disorder and disease.

MPs in England and Wales want to follow suit, and then some. So now, on both sides of the border, there is a great deal of support not only for powers to stop cut-price promotions and happy hours, but to prevent supermarkets from selling alcohol at a loss.

However, a large minority object to what they see as yet another intrusion by the nanny state. Adults should be free to do what they want, the argument goes, including drinking themselves into oblivion.

This is where Sartre comes in. Talk of freedom is cheap, but for Sartre, the reality is frightening. To accept that one is free is to accept that no-one can choose your moral values or the meaning of your life for you. It is to accept that we are nothing except what we do, and that all talk of what we could have been, if the dice had rolled differently, is meaningless.

No wonder Sartre thought the biggest threat to freedom is our own refusal to accept it. We would rather blame anything - our genes, star sign, parents, society, our education, the drink, peer pressure - than admit we could do otherwise.

Under the German occupation, the French had less liberty to go, say and do what they wanted. But Sartre thought these limits actually made people more acutely aware of the freedoms they did have.

Sartre may have made too much of this, but his argument does highlight an important distinction between two types of freedom. One is the kind which depends entirely on external constraints: the law allows me to drink at this time or that, or to walk on this land or not. The other is to do with our deeper autonomy: the ability to truly make decisions for ourselves.

The people who complain about the nanny state want there to be as few external constraints on the actions of responsible adults as possible. But I fear they often underestimate the extent to which our very capacity to be responsible adults might sometimes depend on controlling what others can do.

The alcohol debate provides a clear example. Yesterday, we read that the big four supermarkets oppose plans to end price promotions on off-sales and raise the legal limit for buying alcohol to 21 in Scotland. Obviously this is not because they are stout defenders of civil liberties. Rather, supermarkets know that these laws will inhibit their freedom to manipulate the buying choices of consumers.

The supermarkets are not alone on this. Every day we are being fought over by businesses that seek to persuade us, by any means possible, that we really should buy what they have on offer. It would be nice to think that, as intelligent adults, we can be trusted to accept or reject their pleas sensibly. But this is to seriously underestimate our capacity to be influenced, something which Sartre also played down.

So which is really the greater threat to our freedom? Is it laws, enacted by an elected government, that openly tell us how alcohol can and cannot be sold? Or is it corporations, analysing our buying habits, using research in psychology to make us want what we didn't know we wanted, and using every trick they know to get us to buy more and more?

To my mind, explicit restrictions to which we give our consent are much less insidious than the constant, subtle, usually unnoticed ways in which our very desires are being manipulated by those who can gain from them.

Sometimes it is by restricting a little of the wrong kind of freedom that we foster more of the type that really matters: the power to truly think and choose for ourselves.