This series of articles will discuss some of the major moral issues (i.e. relativism, marriage, chastity, respect for human life, contraception, fornication, masturbation, pornography, homosexual acts, abortion and fertility issues) of our culture and how we can know through natural law that these acts are immoral. The purpose of these articles is to show that immoral behavior is something we can know from reason and not simply from the Church or Bible alone. God, however, knowing that our intellect would not know right actions and wrong actions perfectly and immediately (due to our fallen nature), gave us his commandments and, later, his Church to guide us to a thorough knowledge of moral truths. Upon reflection, reason confirms the truths taught by the Church.
Natural law, according to St. Thomas Aquinas, “is nothing else than the rational creature’s participation in the eternal law” (ST I-II, Q. 94). Essentially, God created humans with a specific, unchanging nature and our actions must accord with our true nature, rather than our fallen nature, in order to be moral. Conversely, actions that contradict our nature are immoral. Because we have reason, we are not irrational animals that function on pure instinct. Our ability to reason serves as a check against instinctive actions. We may instinctively desire something, but reason tells us if the desire accords with our nature. Human reason is directed at truth. This doesn’t mean that every individual’s reasoning is always perfect. It simply means we are ordered toward seeking truth, which is why Jesus says the truth sets us free. Free from what? The truth sets us free from lies, because lies are contradictory to reason and, thus, our human nature. Now, the truth would be of no use if we were not obligated to do what is true and right. Therefore, our actions must accord with truth. If we choose to act in a way that contradicts truth, we place ourselves in a state of sin. If we refuse to repent of our rejection of truth until death, we place ourselves permanently outside of Truth himself, Jesus Christ, the only begotten Son of God, the Word, the Truth. Therefore, truth, and our adherence to it, sets us free from lies, sin, spiritual death and, ultimately, hell.
Please understand that natural law does not replace the Church, Bible or God’s commandments. Rather, natural law helps us to see that moral laws taught by the Church, Bible and God’s commandments are true and just. Thus, by dissecting our culture’s frequently committed immoral acts, we will see that these acts are indeed immoral despite contrary opinions asserted by our culture and even by some in our Church. Finally, since God created us with a mind ordered toward truth and sent us his Truth made flesh 2000 years ago, it would be irrational for Jesus to create a church in which church teachings contradict truth or for him to create countless churches that contradict one another. Therefore, Jesus Christ founded one Church to be the pillar and bulwark of truth on earth (1 Tim 3:15). From history, we know this church is the Catholic Church. Thus, it cannot teach error. For, if the church Jesus founded could teach error, then Jesus himself could teach error, but this cannot be. Therefore, we are required to know the Church’s teachings and adhere to them.
For more on natural law, read Catechism paragraphs 1950-1974.