This is part of a couplet with the fourteenth chapter. Paul has been speaking largely to a legalistic Jewish contingent in the Christian community at Rome. He is trying to get across the wonder of Grace and the core of the doctrine of Christ. He sees a lot of nit-picking and schism over rules and reg’s. A lot of disagreement over non-essentials. This is costing the community in terms of peace, essential unity and hope.
In the fourteenth chapter Paul zeros in on holy days, ablutions and food and drink. Some partake. Some do not. This difference of opinion and difference of light shown should not be allowed to break up the Family. He shows how in his own life God convicted him, the zealous Jewish Pharisee, to become messenger to the Gentiles in particular. With that having been accomplished, it would appear that nothing is impossible.
Folks, let us stretch the essentials and shrink the non-essentials in our Communion. This is the thrust behind Jesus’ prayer in John 17.
Enough about that. I would also leave you with the recommendation to read the entire fifteenth chapter to determine whether or not its balance, intent and terminology do not also reinforce our understanding of the concept of Triune God (Holy Trinity – Father, Son and Spirit). I think that you will be enlightened, and as the old Scottish divines used to say “fear your light” (not someone else’s).