Romans 14:23 doesn't say unbelievers choose to do things in a sinful way.
True, for it’s not talking about unbelievers at all. Paul is addressing disputes within the Christian community over conscience, food, and doubtful matters. The fact that we could have someone in this text acting “not from faith” doesn’t identify him as an unbeliever; the “one who doubts” is a brother with a troubled conscience in a disputed matter.
And you are not a brother. You do not belong to the class of persons that Paul is describing in this passage, so you cannot appropriate the verse as though it were speaking about the unregenerate.
It says the act in question constitutes sin if it is done without faith.
Yes sir, which is precisely what I said. To do something without faith, to act against conscience, is to do it sinfully.
The improper motive turns the act into a sin.
There is the
act in itself and the
act as performed. To speak with a little more philosophical precision, there is the act considered in its object, and the act as concretely performed by an agent with a motive and end. Some acts in themselves, if described too thinly, are morally neutral apart from more information. For example, “He took his neighbor’s phone.” That is under-described. Did he steal it, or did his neighbor hand it to him? That makes a difference.
It is the
act as performed that makes it good or sinful, which is what we are talking about. An act may be good in its object yet sinful in the doing of it. For example, giving money to the poor, as an object in itself, is a good kind of act. But if done for idolatrous reasons, then it is sinful as performed. As for the unregenerate, every act is done for idolatrous reasons. Every thought, every word, every act.
However, there are also acts whose object is evil in itself—murder, adultery, idolatry, blasphemy, and so on. These are sinful not merely because of motive, but because the object itself is disordered. In such cases, a person’s motive cannot redeem the act but only compound the sinfulness.
But if, because I'm an unbeliever, you know that I cannot possibly comply with your request without sinning, then you are effectively asking me to sin. You asked an unbeliever for a ride to the store despite knowing there was no non-sinful way he could possibly comply. … If you know the agent cannot possibly comply without sinning, then either you are totally irrational or you want them to sin when you ask them to do anything.
Your argument is epistemic and it fails on two different fronts.
First, I simply cannot know what you claim I know. I may suspect you to be unregenerate by your profession and posture, but I could also be wrong—and I am wrong often enough for that to be likely. I also have no idea whether you are of the elect or not. Why is that relevant? Because I would first have to know you’re not of the elect before I could know that you “cannot possibly comply without sinning.” Why? Because it’s entirely possible for an unregenerate elect person to comply without sinning. God could, in the very moment of the act, regenerate you, grant repentance, and cause the act to proceed from faith. However, whether you are elect or reprobate is something I cannot know.
So, already your argument fails.
To add insult to injury, even if somehow I did know that you necessarily would perform the act sinfully, that still wouldn’t turn my request into me asking you to sin. This is simply a repeat of your original claim, which I already critiqued. Please interact with the distinction I made. Again, what I am asking you to do is some good X (e.g., feed the poor) and you’re choosing to perform that act sinfully (e.g., for idolatrous reasons). The sin lies in your motive and manner of performing it, not in my request. I asked you to feed the poor; I did not ask you to sinfully feed the poor.
The only alternative is, "I knew he couldn't comply with my request without sinning, but I made the request anyway, hoping that he wouldn't sin" is absurd and totally irrational.
It really is absurd, but not for the reason you think. It is absurd because you attribute to me knowledge that no human could possess.
That's a denial of the first point of Calvinism (a.k.a. total inability).
No, it’s not. It is practically a restatement of it, but includes a necessary distinction—that the unbeliever’s inability is moral, not physical or rational. The unbeliever is accountable precisely because he possesses the physical and mental faculties necessary for obedience, yet he nevertheless refuses to obey God or submit to his authority. As Mitch Cervinka put it,
Man’s problem lies in the desires of his heart—he loves sin and hates righteousness—and this is what makes him guilty for his sins. He could obey God's law if he desired to do so. He could trust in Christ if he had any love for God. Man is guilty for the simple reason that, in his sinful rebellion, he refuses to do that which he has the full mental and physical ability to do. His problem is a moral and spiritual problem: he is a sinner at heart, who has no desire for God or godliness.
WCF sec. 3 forces the conclusion that God wants me to answer you the way I actually am. If I'm answering you here the precise way God wants me, I'm so convinced that's good authority that I won't trifle further with you about it.
You are convinced that the
Westminster Confession of Faith is good authority? Really?
Summary: My point stands undefeated: There is no action you could perform while unregenerate that wouldn’t constitute sin.
Non posse non peccare.