Hi, Major 1, it has been a while. As I understand one of the
MAJOR differences of the two is that Protestants believe in direct, Divine inspiration through the Holy Spirit and/or the fact that God's Word/The Holy Scripture is "God breathed" and "living and active." This is the major reason, I believe, that the Protestant fore fathers, Luther and Calvin and others (who were considered heretics by the RCC), were persecuted, imprisoned, tortured and even killed by the Catholic regime during the Inquisitions (see:
What were the Inquisitions?) During one of the four (second:Spanish Inquisition 1478>(over 31,900 killed)) Inquisitions over 2,000 "heretics" were burned at the stake (in less than a decade) These "heretics" were not only being divisive but I think much more importantly they preached a message which threatened the authority (and wealth) of the RCC which had "gotten in bed" with the Emperors of Rome (4th century.) Their influence over the conquered peoples (in effect, the world) of Rome (Roman Empire) enabled the RCC to form a collusion with Rome which was a VERY beneficial symbiotic (and horribly evil in many ways) relationship for both parties: hence, the "separation of church and state" (not: of personal religious convictions and state) in our Constitution. One of the many RCC's benefits was a heretic now became an enemy of the State and the maximum punishment now shifted from excommunication to death and the RCC was given virtually free reigns on how to conduct their Inquisitions. Sorry, for that large bit of info/joy ride.
Anyway, because we "heretics/protestors" believe in direct, Divine inspiration with individual responsibility and accountability and not the Catholic way of always going through what we regard as a worldly religious system based upon the worldly influence and power gained by the collusion described above, like you said, we will rarely (not, never) ever be able to influence a devout Roman Catholic. But we must NEVER< NEVER< NEVER forget that our Protestant forefathers/founders WERE Roman Catholics in high places who, after much study of the Holy Scriptures realized and actualized the Scriptural foundations for direct, Divine individual inspiration. I believe that Roman Catholics, through their fundamental belief in Jesus the Christ and what He did for them, ARE Christian but due to many hurdles thrown in their way they have been crippled (but not totally prevented) from realizing that they are endowed individually with the Holy Spirit and open and free for direct, Divine individual inspiration with individual responsibility and accountability.
Direct, Divine individual inspiration need not always or ever be determined by puny human nature or reason. The Holy Scriptures tells us several times that all Christians are endowed with the Holy Spirit Who can also guide us if we acknowledge and submit to Him.