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The so-called tongues-speaking engaged in today is a form of gibberish called "glossalalia".
This phenomenon is very strong in Caribbean and Brazilian voodoo cults and many pagan religions. It is a means of distracting sincere people from the real message of the word of God.
This phenomenon has been studied extensively by Linguists. There has never been an authenticated case where a tongues speaker has been shown to be speaking a real language. Not ever. If tongues are a sign for unbelievers, then scientists who examine tongues speakers should be very impressed. This phenomenon and the "faith healings" - really "fake healings" - that usually accompany it have been shown time and again to be the work of charlatans deceiving those who desperately want to believe.
I grew up as a Catholic and the Catholic church is a huge believer in faith healing through the "mediatorship" of saints and Mary in particular. The Roman church has been "caught out" many, many times deliberately misleading its flock in this regard. If the "beast" can convince its followers with "lying wonders" it is no wonder that others in positions of spiritual leadership do the same. Many so-called "spirit-filled" evangelists have been shown to be frauds living sinful lifestyles while milking their gullible congregations for millions. There is money to be made in the flashy showmanship that passes for "spirit-filled" religion these days and the lavish life-styles of the current crop of "peddlars of God's word" belie their commitment to Christ. It is astounding how desperate human nature seems to be to put its trust in man.
One must base one's approach to these things on the plain teaching of the Bible. God's word is more reliable than fuzzy "reports" of miracles and gibberish which passes for a true spirit gift.
So, are tongues speakers speaking in a real language when speaking in tongues? No, they are not. Are they deceived? Yes they are.
"To the law and the testimony. If they speak not according to this word, it is because there is no light in them." Isaiah 8:20.
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