Note on Rand

Ayn Rand tries to bridge the is-ought divide by pointing out the base-superstructure relation between the two. The physical world and it's laws are a necessary precondition for the existance of ethical laws - there would be no morality if there were no people.

However, she uses a linier model of superstruture determination by the base. She relies on the notion that the form of the base determines the form of the superstructure. This isn't the way determination works.

The base determines which superstructures cannot spring from it, and to some extend which ones are more or less likely from the vast array of possibilities. Determination is negative, but Rand requires it to be positive.

She also relies on a kind of moral superimperative - that actions be 'life positive'. This is an ethical skyhook, coming from nowhere and determined by nothing - not even the physical base.