"...It is at this stage in her argumentation, at the very point of seeming triumph over subjectivity, that Rand loses the battle. She takes aim at the Humean disjuncture of the prescriptive from the descriptive and fatally wounds the pretentions to objectivity of her own systematic ethics: "The fact that a living entity is, determines what it ought to do. So much for the issue of the relation between 'is' and 'ought'"("The Objectivist Ethics"). In these two sentences, Rand reveals a serious misconception of the nature of the Humean is-ought gap and introduces a dangerous potential for self-contradiction into her own ethical system.
In his work A Treatise of Human Nature, the Scottish philosopher David Hume challenged the basis of all objective systems of morality:
"I can not forbear adding to these reasonings an observation, which may, perhaps, be found of some importance. In every system of morality, which I have hitherto met with, I have always remarked, that the author proceeds for sometime in the ordinary way of reasoning, and establishes the being of a God. or makes observations concerning human affairs: when of a sudden I am surprised to find, that instead of the usual copulations of propositions, is, and is not. I meet with no proposition that is not connected with an ought or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new revelation or affirmation, 'tis necessary that it should be observed and explained; and at the same time that a reason should be given, for what seems altogetherClearly, Rand thinks that Hume denied a connection between facts and systems of morality. This error is not uncommon, and forms the basis for A. C. MacIntyre's revisionist reinterpretation of Hume's famous paragraph. Claiming that Hume could not have meant to establish a total divorcement of facts from values because Hume uses facts in his own ethical system, MacIntyre interprets Hume to be assaulting only theologically-based morality. In fact, there is nothing in the Humean formulation of the problem which hinders the simple integration of facts and values. The sole difficulty arises over the derivability of values from facts...In conclusion, then, Ayn Rand's system of Objectivist ethics does not provide the basis for a solution to the Humean dilemma of the is/ought gap; nor have attempts by a new generation of natural law ethicians to rework her system succeeded in subduing that central ethical difficulty. Since no ethical system has been demonstrated to have solved the is-ought problem, it may be thought a minor flaw in Rand. It is her specific claim to have overcome this difficulty that magnifies its importance in regard to her system."
inconceivable, how this new relation can be a deduction from others, which are entirely different from it."