I know that withdrawal is not considered natural birth control and is not approved by the Church. But…
NFP is natural birth control. The couple uses their God-given intellect to learn about the fertility cycle, and then uses the knowledge gained to modify their sexual behavior by mutual consent. Their aim, in attempting to avoid pregnancy, is to make sure that there are no living, healthy sperm in the woman’s reproductive tract when she ovulates. Every now and then, you may get that extra hardy sperm that manages to outlive the normal lifespan and ends up causing conception. It is in being open to this possibility of life when God wills it to happen that NFP gains Church approval. They cooperate with the design of the human body and the reproductive cycle in order to have some control over when conception happens.
Withdrawal is also natural birth control. The couple uses their God-given intellect to learn about the way conception happens. They they use that knowledge to modify their sexual behavior by mutual consent. Their aim, in practicing withdrawal, is to make sure that no healthy, living sperm make it into the woman’s reproductive tract. Every now and then, you get either bad aim or a really good swimmer, or those few stray sperm in the pre-ejaculatory fluid, that might result in a conception. So why is it that, even with this possibility still there, this method does not gain the Church’s approval? The couple is still cooperating with the design of the human body, in using the man’s awareness of what is happening in his body, and the knowedge that without sperm there can be no baby, in trying to have some control over when conception happens.
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