[jmherbener]

Because this is a philosophical question, I asked my colleague David Gordon who supplied the following answer:

Thanks for this excellent question. If true premises led to contradictory conclusions, we would really be in trouble! Fortunately, your student has I think read Hollis and Nell wrongly. They do indeed defend economic laws as necessary truths,and Hans Hoppe has cited them in support of his own views on methodology. They don’t claim that their analysis of capitalism is based on deductions from self-evident axioms, though. Rather, they incorporate empirical claims about capitalism into their work.