From what I have read about this problem we are called to avoid any anti-christian hedonism in the sex act. This means that any pleasure seeking must not lead to the violation of an obligation that binds under the pain of sin. With the sex act we can group the duties and obligations that pertain to intimacy into three categories.
1.procreation â nothing can be done to destroy the natural procreative nature of the sex act.
2.relief of concupiscence â The use of marital intimacy is supposed to lead to the protection of chastity. Anything that would leave one of the spouses tense and unsatisfied would be sinful pleasure seeking.
3.justice and charity â each spouse must not do anything that causes the other unnecessary pain or repugnance
Obviously, what is attractive to one person might be repulsive to another so it is an area that requires a great deal of sensitivity and compromise. Restraints, while not sinful per se can lead to sin if they are used in a manner that lacks charity or leaves one spouse uncomfortable or unsatisfied.
You can read more about the problem here in âMarriage Questionsâ starting at chapter 10.
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