Christians have a standard. We have a revelation from God, given for us to glorify and enjoy him. This “rule” principally teaches two things:
1. What we are to believe concerning God
2. What God requires of us.
We have a standard. The world does not. It has an opinion and a circular reason for defending that opinion. When I explain this to an unbeliever it never seems to make sense. Why? Because their opinion of my statement is wrong. On what basis? Their opinion.
They claim that my standard is not absolute. That is fine, but it is my standard, one not derived from myself, and not my opinion. In addition, it is a standard that gets me out of vicious circle, as this standard comes from without. Will this convince the unbeliever? No, but only based on their opinion.
Finally, this standard says that the unbeliever knows that the creator of this standard exists. He happens to also be made in the image of God, yet he takes this implanted knowledge and suppresses it. He does so by ultimately making himself God and spewing his own opinions. As those opinions spew in the name of autonomy, the inescapable image he was created in causes him to embrace (and ultimately borrow) morals, values, etc. from the standard, yet calling it his opinion. Will the unbeliever believe this. No. Why? Because their opinion of my statement is wrong. On what basis? Their opinion.