Some people think that nature has intrinsic value, that it has value in itself quite apart from its present and future economic, intellectual, recreational and aesthetic uses. Some people think that nature's intrinsic value grounds an obligation to preserve it and to minimise human interference with it. I agree. It is important, however, to try to say exactly why nature has intrinsic value, to go beyond merely stating some idiosyncratic attitude and to provide some justification of that attitude with which others might engage. Presumably there are properties that wild nature exemplifies in virtue of which it is intrinsically valued. Only when these are indicated is rational debate as to whether wild nature has intrinsic value possible. Only when these are indicated is it possible to begin to persuade dissenters to change their views. Indeed, unless one can at least begin to say what these properties are it is not clear that the attitude could have any meaningful content. While it is perhaps possible to value something without immediately understanding what it is about the thing that makes it valuable, the failure to come up with any candidate value-adding property after some reflection suggests that the initial value-judgment is vacuous.

Williams puts the problem as follows: