Do They Already Know?

"One of the people witnessing with us mentioned later the issue of the holy spirit convicting people, and Romans 2:14 which speaks about the law written on the hearts of men as their conscience, and therefore we do not need to take them through the law because they already know they are sinning and doing wrong."

If that's the case, then later on in Romans 2:21-24, the Apostle Paul wasted his time, when he took his hearers through the Law:

"You, therefore, who teach another, do you not teach yourself? You who preach that a man should not steal, do you steal? You who say, "Do not commit adultery," do you commit adultery? You who abhor idols, do you rob temples? You who make your boast in the law, do you dishonor God through breaking the law? For 'the name of God is blasphemed among the Gentiles because of you,' as it is written."

Also, it's not true according to Scripture or by experience, that sinners know the nature of sin. Look at Paul's own testimony in Romans 7:7:

"What shall we say then? Is the law sin? Certainly not! On the contrary, I would not have known sin except through the law. For I would not have known covetousness unless the law had said, 'You shall not covet.'"

All you have to do to see the reality of what Scripture is saying, is ask an unsaved person if they think that they are a good person. They will almost always say, "I'm a very good person" (see Proverbs 20:6). This is because they are ignorant to God's perfect standard of righteousness. They measure themselves by their own very low moral standard, and come up clean in their own eyes. This is why they need the Law. It's like a mirror that simply reflects the truth.

The Holy Spirit convicts of sin (which is transgression of the Law--see 1 John 3:4), righteousness (which is of the Law), and judgment (which is by the Law--see Romans 2:12, James 2:12). So, if you make the mistake of leaving out the Law, you rob the gospel of its power. You remove the bow from the pointed arrow. It leaves the gospel with no point. The sinner concludes, "Why do I need a Savior if I'm not a desperately wicked sinner?"