Arga Blog's

Ayn Rand 'bridges' the gap between is and ought by denying that such a gap exists. This is a necessary step in her constructing a foundation for objectivist ethics. She proceeds (approximately) thusly:

1. If X's nature is Y, then X ought to strive to be Y.
1a. (If Man's nature is 'rational animal' then Man ought to be a 'rational animal').
2. X is Y.
2a. (Man's nature is 'rational animal').
3. Ergo, X ought to strive to be Y.
3a. (Ergo, Man ought to strive to be a 'rational animal').

The argument appears valid, but are the premises true? I'd like to present a possible counterexample:

Suppose X is a man and further suppose that 3a is true.

Suppose still further that technology is developed which allows X to shed his animal nature; perhaps, he is given the opportunity of having his brain placed in a mechanical body (most would hardly call this animal, but hey maybe so). This body would allow him to live indefinitely and thus to continue to pursue and preserve all that he values. Rand's argument would have all of her followers die.

Also, don't animals, by their nature, die, but posses a will to survive? Is it not also within the nature of an animal to live at all costs? Is the "survival modifier" stronger than the "rational modifier". When a situation arises in which elements of some entity's nature are in opposition, one would think that one of the elements would need to supercede the others. Certainly, there are situations where 'rational' and 'will to survive' would clash (eg, a boy who is starving to death and needs to steal food -- yes, he has begged and tried everything else).

But really, we need to discover whether premise 1 is true. I don't remember her spending much time defending it, but I will investigate it. As someone else -- A Fyfe -- pointed out, it almost seems as if Rand is attempting here to define ethics into existence.