And now each "believer" is made perfect in his or her faith?
Yes
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What evidence do you have that the Holy Spirit guides all "believers".
The Holy Spirit only guides if a person is willing. GOD lets all have free will and a choice to chose HIM.
Acts 1:[8] But you shall receive power when the Holy Spirit has come upon you; and you shall be my witnesses in Jerusalem and in all Judea and Sama'ria and to the end of the earth."
[16] "Brethren, the scripture had to be fulfilled, which the Holy Spirit spoke beforehand by the mouth of David, concerning Judas who was guide to those who arrested Jesus.
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And if He does, why the plethora of beliefs?
Freewill, human nature...
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The Holy Spirit does guide us, either through His Church or to His Church and always in His own time His manner and for His own purpose.
Absolutely:)