"A Kantian or even a semi-Kantian cannot permit himself to value anything profoundly, since an inexplicable "duty" may demand the sacrifice of his values at any moment, wiping out any long-range plan or struggle he might have undertaken to achieve them . . . .
The notion of "duty" is intrinsically anti-causal. In its origin, a "duty" defies the principle of efficient causation - since it is causeless (or supernatural); in its effects, it defies the principle of final causation - since it must be performed regardless or consequences."
~ Above found at Ayn Rand Lexicon - Duty