In other words, does a valid profession of faith have to be deemed real, by those baptizing, as being the reason one would baptize a person even if the person professing is not sure of that profession? Has any credo run into this problem? If so do you wait to see some assurance comes before you baptize?
Assurance is a fickle creature. I met with a brother in church the other day who is struggling with his assurance. I asked him, "what do you confess"? Do you confess you are a sinner? Do you confess that Jesus is the Son of God? Do you confess that he suffered and died on the cross to atone for sin? Do you confess He was buried and on the third day rose from the dead? Do you confess that He is coming again? I can go on. He answered in the affirmative. He believes and confesses those things in spite of how he felt. I had a similar conversation with a candidate for baptism two years ago. This young lady was concerned that she doe not always act as a Christian. I went through the same exercise. She also believed and confessed all those things. I counseled her that her tender conscience towards sin was a good sign when coupled with what she confessed about the Gospel. She decided to be baptized. While a dry head knowledge of the facts is not grounds for assurance (even the demons believe and shudder), genuine belief in spite of feelings is.
Of course each person, and each situation, is different. If a candidate for baptism is struggling with their assurance because they are engaged in unrepentant sin, then that is an issue that needs to be addressed. Such a situation would belay a credible profession. But that aside, for the reasons given earlier, I would spend time with that person asking them what they believe and confess about the Christian faith.
While assurance is not of the essence of saving faith, I would be uncomfortable baptizing someone at a time when they had no assurance. "Whatsoever is not of faith is sin" (Rom. 14:23). If they are unwilling to receive baptism because of their remaining doubts, I would endeavor remove whatever obstacles exist, but I would take my time. We should avoid haste in making such a determination. I would continue to work with them to determine what exactly their lack of assurance rises from. They may have good reason to doubt their interest in Christ. In which case you would not want to baptize them. If in time you discover it lies more in some deficiency in their thinking, you can help address that and bring them to the waters of baptism with more understanding, assurance, and joy.