Beware! They are leading up to the Sabellianist heresy (Sabellianism) or as Jude Thaddeus said, “modalism”.
Sabellius was a Priest around 200 A.D. who turned into a heretic manufacturing phony denials of the Holy Trinity.
This cuts to the core of who God is (and isn’t).
Catholic Encyclopedia The Monarchians properly so-called (Modalists) exaggerated the oneness of the Father and the Son so as to make them but one Person; thus the distinctions in the Holy Trinity are energies or modes, not Persons . . . .
Tim Staples is a Marine who is also a Catholic Apologist (“Once a Marine always a Marine” but I guess some people would call him an “ex-Marine”).
Tim Staples talks about the Sabellianist heresy (
here) when he is discussing the Oneness Pentecostal Minister who was so confused regarding his Baptismal formula, that this minister incorporated three formulas to Baptize a person.
Sabellianism is sometimes called “Oneness Pentecostalism”. Before becoming Catholic, Tim Staples dealt with Sabellianists when he was going to Jimmy Swaggart Bible College (I think it is now called World Evangelism Bible College but I may be wrong on this).
Initially Staples didn’t know how to defend Christianity against the Modalist heretics. Staples talks about how he turned to reading the ancient Church Fathers to find out how to effectively refute this heresy.
Staples has several versions of his conversion Testimony to Catholicism. All are great. An inexpensive MP3 download can be found
here.
A more detailed 3 CD set can be found
here.
Staples is one of the funnest and most knowledgeable Catholic Apologists you will ever hear (I guess we could call him a “Funnest Catholic” as opposed to a “Oneness Pentecostal”).
I would suggest listening to the Youtube link right away (above or again
here) and taking it from there. You could put this audio on in the background while checking your email, doing work around the home, etc. If you give Staples 5-10 minutes, he will draw you in with his speaking style (at least he does me).
It looks like he also has this talk posted
here.
See also
this Catholic Answers Tract.
Hope this helps.