Earlier this week, Zoe Williams did a sterling job debunking the latest nonsense from the Girl Guides, who have announced that they will no longer "serve God" but instead "be true to themselves". Neither Williams (an atheist), nor I, have a problem with dropping the God bit. We now live in an increasingly irreligious society etc. I totally get it. But come on, what on earth does being true to yourself actually mean?

I take it as something like this: be an individual, think for yourself, don't follow the crowd, everyone has a right to live by their own sense of what is fundamentally important. Cue Frank Sinatra. That this is the dominant moral outlook of our age is illustrated by the fact that My Way remains one of the most popular choices of song at funerals – though it is telling that My Way seems to be so many other people's way as well.

As ever, Life of Brian has it about right. "Please, please, please listen. I've got one or two things to say. You don't need to follow me. You don't need to follow anybody. You're all individuals." "Yes," the crowd replies in perfect unison, "we are all individuals." That's what the new Girl Guide pledge (said in perfect unison, of course) will sound like to me. It's a general rule of thumb: we are at our most conventional when we think we are being most unique and different.

But there is also a philosophical problem with My Way, brilliantly diagnosed by Charles Taylor in his The Ethics of Authenticity. We choose certain values because they are important, he argues, but things are not made important simply because we choose them. Choosing values does not, indeed cannot, make any sense in a cultural vacuum. We require what he calls a "horizon of significance" against which we are able to make choices in the first place. In and of itself, choosing does not confer worth, for there has to be a basis on which one makes a choice, some reference to wider significance.

Ironically, if choosing one's values is just some mysterious feel thing conducted in the isolated crucible of the disengaged self it becomes little more than an emotional lucky dip, easily manipulated by forces outside the self that are not being critically examined. No wonder "being true to yourself" has so little resistance to the power of advertising. It is not coincidental, for instance, that the catchy My Way is currently being used as the tune of an advertising campaign for the latest Golf GTI – a film of lots of people singing the same song with the hope that they will all buy the same car. A sense of self that has disengaged itself from the stability of wider social, historical and cultural concerns is easily conscripted by the ferocious power of modern capitalism. Without the protection of such hedges, we suffer a gradual form of existential soil erosion until nothing interesting is ever able to grow. Those who vigorously pursue the "true to yourself" line might eventually find that they end up not having much of a self to be true to.

From the Reformation to the cultural revolutions of the 1960s, western thought has rightly rebelled against those who would impose values from without. But the problem here is that who I am also comes from without – from parents, from friends, from history etc. To seek to become the exclusive author of one's own identity, Nietzsche style, is to make the self smaller, weaker and thus, ironically, more compliant. In other words, we have rebelled against the sources of rebellion and so return to the shopping centre in our ripped jeans feeling like mini-revolutionaries when we are really about as revolutionary as that great pin-up of "true to yourself" philosophy, Charlie Sheen. It would be funny if it wasn't so serious. Another form of despotism is now upon us.