There are some things that are a matter of conscience. We’re not talking about activities that are clearly sinful, but those things that people could have differences of opinion on. Apparently, some Jewish believers were having trouble leaving the dietary laws and the festival/feast days behind. Paul states that whatever you do, you do it because you want to bring glory to God since our lives are His from beginning to end (14:6-8). We shouldn’t judge others who think differently, because God is the final judge (14:9-12)!
And, since we are living together in community (with particular emphasis on Jews and Gentiles getting along), we shouldn’t want to cause distress to someone else, particularly if they view an activity as sinful (14:13-23). For example, in our day and age some believe that drinking alcohol is wrong, while others believe it is ok. Those who believe that it’s ok shouldn’t flaunt their belief or engage in drinking around people who don’t.
Does 14:23 describe a spiritual truth or an emotional reality? Since a lack of faith dishonors God, a failure to follow through on personal beliefs could be considered sin. However, it’s also possible that the person’s own conscience is condemning them because they believe they are engaging in a sinful activity. So, is it guilt, sin, or both? Most commentaries tend to believe that it is actually sin.