Father is correct that one must have sufficient reasons for using NFP. But then he makes the mistake of equating NFP with periodic continence; they’re NOT the same. NFP is a way of determining fertility based on certain physical signs of the woman’s fertility. And then, based on those signs, a couple may determine if they have sufficient reason for having the marriage act at that time or abstaining (remember, NFP can also be used to achieve pregnancy). But when this priest cites author Greg Popcak’s recommendation that couples practice NFP every month to discern if they’re being called to have another child and says Popcak’s recommendation is wrong, it’s evident that he’s wrongly thinking Popcak is exhorting couples to practice periodic continence each month, which just isn’t the case.