Volumes have been written on this topic and a blog post can only barely scratch the surface, but hopefully this can be a first step in deepening your understanding of the purpose of our human sexuality.
Sexual intercourse was designed by God and like everything He made, it was designed to be very, very good. As with anything God created, it is most beautiful and fulfilling when it’s used the way God designed it to be used.
There’s a concept in philosophy called “teleology”. The teleology of a thing is its purpose for existing. My colleague Jenny has the best (or at least most relatable for me!) analogy to explain teleology. Say you got this incredible designer coffee mug for your birthday and you take it to work and put it up on a shelf so everyone can see it. It might look really nice up there but it’s not fulfilling its teleology, it real purpose. Now say you take it off the shelf and clean it up and set it on your desk and put your pens in it. Now it’s closer to fulfilling its teleology because it’s holding something but it’s still incomplete. Now say you take your pens out of it and wash it out and fill it with a really incredible flavor of coffee, complete (for me!) with a generous serving of rich cream. Now it’s really really close to fulfilling it’s teleology because it's holding a beverage. And when you’re drinking and enjoying that perfect cup of coffee out of your beautiful mug, it’s now completely fulfilling its teleology.
On a more serious level, our sexuality has a teleology, ordained by God, to be both procreative and unitive. The unitive aspect is what binds a man and woman together, it’s physically pleasurable, helps them grow in intimacy, connects them deeply on a spiritual, physical and psychological level. Sex was also designed to bring forth new life and continue our species. Contraception has taken the teleology of our sexuality and torn it apart. You can now have one aspect of your human sexuality without the other – the unitive part but not the procreative part. And the consequences of course are much more dire when we ignore the teleology of our sexuality than with our coffee cup.
Two terms can be used to describe two very different approaches to human sexuality: genito-centrism and cerebro-centrism .
Genito-centrism is an understanding of human sexuality that totally and completely revolves around genital contact. There’s focus on the physical and external. Genito-centric attitudes divorce the unitive and procreative aspects of intercourse. It says: “I want part of who you are but not all of who you are”. I want the part of you that gives me pleasure and services me in a way I enjoy but not your fertility, the part of you that has creative potential and could bring about the life of another human being. It compartmentalizes the genital aspect of sexual intercourse. The de-personalization that this causes leads to de-humanization of your sexual partner and ultimately psychological and spiritual deprivation. Abortion, pornography, family violence, STDs (STIs) and divorce are all natural consequences or outcomes of a genitocentric mentality and approach to human sexuality and viewing the human person as an object to be used as a means to an ends.
Cerebro-centrism is an understanding of human sexuality that focuses on the human person in his or her totality. It incorporates a person’s fertility into the wholeness of who they are. It views fertility as a part of health, not disease. It maintains the connection of the unitive and procreative aspects of sexual intercourse. This leads to the physiological and spiritual affirmation of each other (“You are good. Every part of you is good. I want to give every part of me to every part of you”). It’s multidimensional and fulfills the spiritual, creative, intellectual, communicative and emotional aspects of our full human sexuality. It respects the dignity of men and women and promotes marital bonding.
When coffee cups are used contrary to their teleology, they are likely to break. Once glued back together, they'll probably leak and can never fulfill their teleology. But this is where the analogy runs dry. Because as humans, we can be healed and put back together by our Redeemer who makes "all things new" (Isaiah 43) and can make you whole again. It's never too late. Using a natural means to understand your fertility and make choices about family planning, like Creighton Model, that works in harmony with the way your sexuality was designed is a really important step in fully becoming the person you were designed by God to be in your marriage.