You sure like to side step questions. My question to you was to define essential doctrine. Cornelius was not brought to Christ via essential doctrines and neither were the apostles. Cornelius and the apostles were brought to Christ via faith and faith alone since only by faith is one saved.
Also you are once again contradicting yourself since you posted that the Holy Spirit deals with individuals and their faith.
Romans 10:7-10
8 But what does it say? "The word is near you, in your mouth and in your heart"-- that is, the word of faith which we are preaching, 9 that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you shall be saved; 10 for with the heart man believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation. NAS
As to the commentary I quoted you are refusing to get past "essential doctrines of Christianity".
[Depart from the faith] Aposteesontai (NT:868) ... tees (NT:3588) pisteoos (NT:4102). They will apostatize from the faith, i.e. from Christianity; renouncing the whole system in effect, by bringing in doctrines which render its essential truths null and void, or denying and renouncing such doctrines as are essential to Christianity as a system of salvation. A man may hold all the truths of Christianity, and yet render them of none effect by holding other doctrines which counteract their influence; or he may apostatize by denying some essential doctrine, though he bring in nothing heterodox.
Catholicism is a
system of esstential doctrines as are the LDS, JW's and etc. What distinguishes these three and other false religions is they either add to God's truth or deny portions of God's truth resulting in the nullification of "salvation by grace through faith in Jesus Christ". Now since religions are made up of people who accept heretical doctrines what this commentator is addressing is apostasy, which is what this thread is about and totally disproves OSAS.
How can a believer be lead by the Spirit without doctrine? There is a simple and Biblical response to your question:
John 14:25-31
25 "These things I have spoken to you, while abiding with you. 26 "But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all that I said to you. 27 "Peace I leave with you; My peace I give to you; not as the world gives, do I give to you. Let not your heart be troubled, nor let it be fearful. 28 "You heard that I said to you, 'I go away, and I will come to you.' If you loved Me, you would have rejoiced, because I go to the Father; for the Father is greater than I. 29 "And now I have told you before it comes to pass, that when it comes to pass, you may believe. 30 "I will not speak much more with you, for the ruler of the world is coming, and he has nothing in Me; 31 but that the world may know that I love the Father, and as the Father gave Me commandment, even so I do. Arise, let us go from here. NAS
Jesus said that some would fall way and only "he who endures to the end shall be saved", which the Holy Spirit explicity revealed to Paul in 1 Timothy, a fact you refuse to accept.
Faith is the only essential Christian doctrine all other doctrines not based on walking by faith are manmade doctrines and/or doctrines of demons.