I used to watch a preacher on TV, Basel Barret Baxter of the Campbellite Church of Christ. He admonished everyone to get baptized by immersion for “remission of sin”. He then ended his message with ...”If there is no Church of Christ near you, a friend can do it for you”.
I’ve often wondered, if a person who is non Christian or even a pagan, can they baptize someone in the name of the Trinity? I have NEVER seen it anywhere in Scripture. And what if that “friend” is a secret devil worshiper or mormon?
Hard to imagine a Satanist INTENDING a valid baptism, though.
Mormons do not believe in the Trinity as Christians understand it. They believe that there are many, many gods; that the Father, Son, and Holy Ghost are three gods; that they came into existence via procreation ---that is, the three gods all had parents who are gods, themselves--- and that these three gods decided to form a unity which the Mormons usually call "the Godhead".
So no, Mormon baptisms are not valid.
Baptism by virtually every other Christian ecclesial community or denomination IS valid, because except for Mormons, most other Christians share in the Catholic Church's understanding of "Trinity."
According to my priest, yes. The baptizer does not have to be religious if the form is correct.
I remember him mentioning times when baptism isn’t even strictly required. Lets say a person is waiting to be baptized and had been going through the preparations - attending church, professing faith, reading the Bible, changing their lives to conform to God’s word.
If that person were to die for their faith, as some Middle Eastern Christians are doing, and as many early Christian martyrs did, it is termed a Baptism of Fire - the desire and transformation were there, even without the actual baptism.
Being willing to die for Christ is showing a true conversion of the heart.
As far as the Catholic church is concerned, the answer is yes, provided they have the proper "intent". The proper intent is to intend to do what the Church does, that is, to administer Trinitarian Christian baptism.
Remember, the spiritual effects of a sacrament come from Christ, not from the minister of the sacrament, who is just an agent or intermediary. Neither does it come through the faith of the minister.
However, this gets tricky if the minister is, e.g., a Mormon or JW. Those sects use the correct words, but do not mean by them what the Church means (because they reject the Trinity), so they are assumed not to have the proper intent.
However, if someone were baptized by a Mormon, and had a signed letter from the Mormon indicating that he or she intended to administer orthodox Christian, Trinitarian baptism, I think it would hard to argue that that baptism was not valid.