Here’s a nasty example – Bestiality is wrong not because it is disgusting or impolite or unhygienic, but because for a human to have sex with an animal is against the natural order, and also because God condemns it.

To take a more ordinary example–lying is wrong because it goes against nature. How so? Because nature teaches us that there is such a thing as truth. To exist in the world, to communicate, to make sense of anything at all there must be such a thing as truth. I must be able to say, “This is a chair. This is not a desk. That is a desk.” My ability to say this and for you to hear this means there is truth and that the concept of “Truth” is so natural and fitting and basic to our existence that it is natural. To lie, therefore, is to do something against nature, and God also says, “Do not bear false witness.”

Anything that is sinful, therefore is against nature or against God’s commandments or both.

This is where it gets interesting:

The natural order and God’s commandments are in place to bring us, as much as possible, to find happiness, wholeness, healing and an abundant life.

The natural order and God’s commandments are designed to make us happy.

A thing is sinful therefore if it destroys or undermines our greatest good and greatest happiness.

The Church teaches that a thing is sinful not to make us feel bad–not to make us feel guilty and ashamed, but to correct those things which destroy the chance we have for the greatest happiness. It also points out the mistakes we make looking for happiness. We not only choose the things which might undermine our greater happiness, but we choose false paths of happiness and choose things which seem to make us happy, but which destroy or damage us or other people or society.

The more we understand these basic principles the more we will be at ease with our choices and make rational choices for the greater good and greater happiness of ourselves, our families and our society.

When we fail our failure is not just “doing something bad”. Instead what is “bad” is something that has undermined a greater good or something that will lead to our ultimate unhappiness and even death.

What is “sinful” therefore is something which damages us and the church warnings about sin are simply a good Mother warning her kids not to play with fire lest they get burned.