In June 1940, fleeing the advancing Nazis, de Lubac left Lyon with a bag which included the notebook for Surnaturel, on which he worked for several days.
De Lubac stated in later years that the book had taken sufficient shape by 1941 to be ready for review; the nihil obstat was granted in February 1942.
Neither the Fathers nor the scholastics, therefore, ever envisioned the possibility of a purely natural end for human persons attainable by their own intrinsic powers of cognition and volition.
[4] De Lubac argues that this unified vision began to unravel in the thought of theologians such as Denys the Carthusian and, more pertinently, Cajetan.
Cajetan, however, while making a similar argument to Denys, did so while claiming simply to be commenting on Thomas: he therefore introduced the idea of human nature as "a closed and sufficient whole" into Thomism.
Although, de Lubac argues, the system of 'pure nature' was perceived to be a novelty when it first developed, it eventually came to be taken for granted, such that, by the twentieth century, rejecting it became synonymous with denying the gratuity of the supernatural.
In the early 1960s, however, his ideas became more accepted in the Catholic hierarchy, and he was among the first summoned by Pope John XXIII to help draft the texts for Vatican II.