Why does the Catholic Church allow family planning using natural means but condemns family planning employing artificial methods as [gravely disordered] (edited by 1ke for correctness)
Because, simply, the church does not teach it is immoral to plan your family or to avoid having children for some period of time due to serious reasons.
The church only teaches that contraception is an immoral means of planning your family. Abstaining when you have a reason to avoid children has always been an acceptable means. Newer deveopments in science allow us to abstain fewer days than in years past. But abstinence remains the only valid means of spacing children.
Why?
Because each act of intercourse must be as God designed it-- both unitive and procreative.
No one is ever required to have sex with any particular frequency-- but every time you do engage in the sex act with your spouse it must be a complete act of unaltered sex.
That is the difference between abstaining and contracepting.
Here is a post I have posted in the past:
NFP and contraception are both methods of birth control. Birth control is just the spacing & planning of children.
The Church does not teach birth control is immoral. The Church teaches that contraception is an immoral means of birth control. Big difference.
Each marriage act (act of sexual intercourse) must be unaltered before, during, or after the act. No action may taken to alter the act because each act must be objectively unitive and procreative in order to be authentic and properly ordered as God designed.
Subjectively that particular act may or may not be procreative. For example, if someone is naturally infertile due to time of the month, post-menopause, already pregnant, etc, then an unaltered act of intercourse is objectively procreative but subjectively does not result in conception.
How does NFP meet this criteria? In NFP each marital act is objectively unitive and procreative. If you have reason to avoid pregnancy you
do not engage in the act. That respects the objective elements that must be present in every act.
How does contraception fail to meet this criteria? When contracepting a couple engages in the marital act while simultaneously altering the act to nullify it’s procreative element-- either before, during, or after the act. Before-- sterilization, Pill, sponge, diaphram, condom, IUD. During-- withdrawal, masterbatory acts that don’t culminate in intercourse. After- morning after pill, abortion. All of these things alter the act either in anticipation of, during, or after.
NFP says: Don’t want to become pregnant at that time? Abstain and respect the act as God created it because we and the act serve God. Engage in the act when the woman is naturally infertile and never alter the act.
Contraception says: Don’t want to become pregnant? Have sex and mutilate the act because the act serves
us.
NFP is not an alterative to contraception, it’s an alternative to complete abstinence.
shameful, vicious and a horrible crime?
The Church does not teach any of the above regarding contraception.