Abstract
The author discusses natural law reasoning, from the 1960s in the context of Pope Paul VI’s Humanae vitae, to recent cultural and intellectual currents and their influence on the tradition. The challenges that have skewed acceptance of a common human nature and the existence of natural law are
addressed. The author shows how the debate on contraception initiated this challenge against natural law reasoning and led to a more evolutive concept of human nature. Attention is drawn to a need for natural law theorists trained in both modern science and Thomistic philosophy to engage the different scientific fields to clarify, adapt, rethink, and even modify the natural law language in accord with the latest discoveries compatitible with evolutionary findings.