"I initially came to know Tierney through reading one of his most important works, The Idea of Natural Rights: Studies on Natural Rights, Natural Law, and Church Law 1150-1625 (1997). For a long time, the scholarly consensus held that the idea that individuals are bearers of rights was essentially a creation of modernity and the various Enlightenments. Rights, according to the British-Australian political theorist Kenneth Minogue, were “as modern as the internal combustion engine.”
Tierney’s book challenged that position. He marshalled extensive evidence to show that the notion of subjective rights first emerges in the writings of canon lawyers as early as the twelfth century and subsequently developed over time. Tierney wasn’t the first to make this case. Nor was it the first time he had touched on the topic. In an earlier work entitled Medieval Poor Law (1959), he had written about the rights of the poor in the Middle Ages. But Tierney’s Idea of Natural Rights outlined the argument in so much detail and with sustained attention to such a wide scope of theological, philosophical and legal sources that he effectively helped to shift the burden on proof to those who took a contrary view."