101 They are greatly deceived who having underestimated or neglected these means which rise above nature, think that they can induce men by the use and discovery of the natural sciences, such as those of biology, the science of heredity, and the like, to curb their carnal desires. We do not say this in order to belittle those natural means which are not dishonest; for God is the Author of nature as well as of grace, and He has disposed the good things of both orders for the beneficial use of men. The faithful, therefore, can and ought to be assisted also by natural means. But they are mistaken who think that these means are able to establish chastity in the nuptial union, or that they are more effective than supernatural grace.
Source: Casti Connubii (Vatican.va)