Can NFP be a grave sin?

[tac]

I am posting this with regards to a question that was asked last week. I had always heard that NFP could be mortally sinful if used with a contraceptive mindset, or without a sufficiently porportionate grave reason. Fr. Serpa responded that he was in agreement with Kimberly Hahn’s assessment that NFP could at most only be a venial sin. This is quite confusing to me, because of the following quote, “Therefore, to embrace the matrimonial state, to use continually the faculty proper to such a state and lawful only therein, and, at the same time, to avoid its primary duty without a grave reason, would be a sin against the very nature of married life.” This is a quote from Pope Pius XII in a letter to midwives. I respect Fr. Serpa and his answers and advice, but my question is how can something that could possibly be a “sin against the very nature of married life” never be a mortal sin? I would appreciate any clarification that you could provide. Thank you and God bless.

 

[Fr.Vincent_Serpa]

Dear tac,

It’s good that you wrote because it forced me to check further on the matter with one of my Dominican confreres who is a moral theologian. His answer: For a husband and wife to selfishly refuse to have children is a mortal sin—quite apart from whether they use NFP or not. NFP is a technique that of itself is morally neutral.

The key word here is “selfishly.” It is possible for a husband and wife to determine not to have children for reasons that are not selfish, e.g., financial or health reasons.

Fr. Vincent Serpa, O.P.