What is the role of the Christian witness in a baptism ceremony? And does he/she have the same responsibilities as the true godparents in helping to raise the child in the Catholic faith?
The role is that, if it becomes necessary for some reason, the witness can testify to the fact that the baptism did happen. For example, if a fire destroys the records, the witness can attest to the baptism.
And does he/she have the same responsibilities as the true godparents in helping to raise the child in the Catholic faith?
No the Godparents have a special responsibility to help the parents, one that is unique to that role. The witness does not necessarily have that, although one could make such general statements as “everyone has a responsibility to help all parents.”
A witness to baptism is not Catholic, and so the Church does no put impossible burdens on them, expecting them to pass along something which they do not have.
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