The two documents are Casti Conubii and Humanae Vitae. Neither provide a list of grave or just reasons. You have to read the entire encyclicals and understand what the Popes are teaching. The primary reason, in both cases, is to teach that the Lord has included us in His plan for the creation of life, which is the end for which the sacrament of marriage was created. As a reward for cooperation in this sacred alliance, he gave us the physical pleasure of the marital act. To thwart the act of conception by physical or artificial means has always,of course, been deemed sinful by the church, and that is reinforced in both documents.
I agree with you here, and I’d like to add something: the Church knows that times have changed and with it changed the means by which families have the ability to support and sustain themselves. These days both parents work in the majority of families, though a family is quite lucky when they can afford one parent to work while the other parent stays home to maintain the household. However, depending on where one lives, even with both parents working, making ends meet can be quite challenging. And by this I mean paying for electricity, water, gas (if that’s what maintains your stove and heat), clothing, medications, groceries. The Church knows this and knows that responsible parenting means more than just fulfilling the responsiblity to “increase and multiply”. It doesn’t end with the birth of a child but continues until the child is no longer a child and is independent. The Church did not create a list of “grave” reasons for using NFP to space out or delay pregnancies because those variables change from family to family and from region to region (which affects said family’s capacity to sustain itself).
It’s disheartening to hear people claim that the Church wants people to have a child a year for as many years as possible and that using NFP is sinful. The Church would
like it if you would have as many kids as possible for as long as possible, but does not strictly require it and allows couples to make that decision considering their circumstances, and we have the encyclicals and CCC to prove it.
And I’ve seen this turn people away from the Church over this misinformation, which is
so unfortunate. This is what makes people throw in the towel and say, “so what, the Church is too old fashioned, and I can’t take them seriously”. I’ve seen people go on contraception because the “teachings of the Church” were too unreasonable (which it’s NOT). With all due respect, and not offense intended, there
is such a thing as being “holier than the Pope” and reading into (and above and beyond) the teachings provided as a guide to us. The Church does
not teach to have children to the point of going mad with activity in one’s home. The Church does
not teach to have so many children that one cannot provide the emotional, spiritual and financial support that each and every child deserves. What the Church does teach is to have as many children as one is capable of providing for, and using NFP to do so: this is a very big part of “responsible parenthood”.
Grave reasons will vary from family to family and the Church knows this. It is not up to outside individuals to intervene in the decision making process (and decisions) of another family. It’s up to each family, with prayer and a LOT of thought, with consultation of their priest.: One woman can be exhilarated by the bustle of 6+ children running amok at home and finds a way to maintain ordered chaos and provide all that each child needs. And that’s so awsome. In fact, she’s my hero. I can’t even express how wonderful that sounds to me. However when another woman feels compelled to seek out phychological intervention because the anxiety of having 2 children running amok in the house is causing her to fear discipling her children because she’s afraid of crossing the line leading to abuse, I would think that yes, this is a “grave” reason to postpone having more children. And yes, I’ve seen this in my life too. We all have our limits. Not everyone is the same.
The ability of the persons taking care of the children is one such “grave” reason to consider. So is the health of each parent. So is the ability of the parents to provide the one-on-one time with each child brought into the family. So is the ability of the parents to provide food, shelter and other necessities for each child. You won’t hear any argument from me about video games, because I won’t have one in my house. But what some people regard as “extras” is essential to other people. Parents want (and should want) to provide an enriching life for their children.
Continued…