Did Paul commit The Appeal To Nature fallacy when he talked about homosexuality in Romans 1? Seems like his reasoning there for thinking it's sinful is because it goes against nature.
“For this reason God gave them up to dishonorable passions. For their women exchanged natural relations for those that are contrary to nature; and the men likewise gave up natural relations with women and were consumed with passion for one another, men committing shameless acts with men and receiving in themselves the due penalty for their error. And since they did not see fit to acknowledge God, God gave them up to a debased mind to do what ought not to be done.” – Romans 1:26-28
But something isn't bad simply because its unnatural. Neither is something good simply because it's natural. Did Paul commit The Appeal To Nature Fallacy? If he did, then The Bible is not inerrant.
Paul’s Argument Is Teleological
I think what Paul is getting at here is that homosexuality is wrong because it goes against the intended design of the human body.
The Bible teaches that God's design for human sexuality was for intercourse to occur between a man and a woman within the confines of marriage. Any sexual activity that isn't between a married man and the woman whom he married is sinful in the sight of God be it homosexuality, masturbation (with or without pornography), pre-marital sex or orgies.
"That is why a man leaves his father and mother and is united to his wife, and they become one flesh." - Genesis 2:5
"Marriage should be honored by all, and the marriage bed kept pure, for God will judge the adulterer and all the sexually immoral." - Hebrews 13:4
“Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor men who practice homosexuality, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the kingdom of God. And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.” – 1 Corinthians 6:9-11
"We also know that the law is made not for the righteous but for lawbreakers and rebels, the ungodly and sinful, the unholy and irreligious, for those who kill their fathers or mothers, for murderers, for the sexually immoral, for those practicing homosexuality, for slave traders and liars and perjurers—and for whatever else is contrary to the sound doctrine." - 1 Timothy 1:9-11
Paul’s argument is teleological; what God’s purpose was for human sexuality. Homosexuality goes against God’s intentions for human sexuality. As cliché as it sounds, He made Adam and Eve, not Adam and Steve. He intended for sex to be only between a husband and wife. Not between boyfriend and girlfriend. Not between boyfriend and boyfriend or girlfriend and girlfriend. Not between boyfriend, girlfriend, and her sister. Not even between husband and husband or wife and wife. But between husband and wife. That was God’s intention for sex between 2 humans.
Moreover, just looking at the design of our sexual organs would hint that homosexual behavior goes against what it was made to do. A tire wasn’t designed to be used as a plate. Shoes were not designed to be flower pots. In a similar way, sex was not designed to be between a man and another man.
Did Paul Commit The Appeal To Nature Fallacy? No. He wasn’t saying homosexuality was a sin because it didn’t occur in nature or because it was unusual. He said it was a sin because it defied the natural order (i.e God’s plan).
On The Christian Worldview, All Morality Is Judged By God’s Character and Commands
Moreover, all morality is judged by God’s character and commands. Something is morally right or wrong not on whether it’s found within nature or not, but whether it’s in accord with the character of God and ergo the commands of God. Often times Christian Apologists (myself included) will argue for God’s existence on this very premise. If God does not exist, there is no ontological foundation for objective morality. And yet, we all know that certain things are right and wrong, that objective morality does exist. But in that case, it follows by modus tollens reasoning that God exists. I go into this argument in great detail in my upcoming book Inference To The One True God: Why I Believe In Jesus Instead Of Other Gods.
As a Christian, it’s highly unlikely that Paul would try to find a source outside of God for determining whether something was right or wrong.
Paul wasn’t committing a logical fallacy. He was just being a good Christian; acknowledging that anything that goes against God’s creative order is sinful.