Most Christians wrongly believe the Gnostic heresies of the 1st century were roundly expunged and condemned by "the church world". While it is true the 1st and 2nd century believers rejected all forms of Gnostic heresy, their belief, rooted in Platonic thought, has crept back into Christianity. It is helpful to first analyze what Plato actually taught to better understand Christianity's modern and most prevelant influence.
Plato lived about 400 years before Messiah walked the earth. He was a student of Socrates but did not promote many of his teacher's beliefs. Plato taught many things, but the thrust of his philisophical world view was that spiritual things were better while physical things were worse. This sounds like a pretty vague idea to us Americans, but it was revolutionary thought in the Greek world. Plato taught the heavens -- composed of ether -- were more substantial than the physical world humans inhabit. Eating, sleeping, sex, work and any other phsyical activities were not as important or valuable as spiritual concepts of honor, trust, prayer and so on. While the concept sounds intresting, it has had devestating effects on Christianity.
In the 1st century, Platonic thought pervaded the Roman Empire. The early congregations rejected Platonic thought as it sought to invade YahShua's Teachings under the guise of Gnostic heresy. Again, Gnosticism, like Platonic thought, taught many things, but its primary thrust was the idea that spiritual things and ideas were better than physical things. A major Gnostic belief was that while a person's spirit man was in heaven, his fleshly man could sin because his spirit man was already safely enthroned above! This led to all kinds of debauchery amongst the Gnostics. Since their spirit man was already saved in heaven, if their flesh sinned, it didn't matter. This belief was so heretical, the Apostle Yochanan spent a whole letter confronting this heresy and tearing it apart in his first letter.
While the early believers, under the guidance of Apostle Yochanan and his disciple Polycarp, rejected Gnostic thought, it eventually seeped back into Christianity. Today, many denominations teach that Christians sin all the time, but the Blood of Jesus still covers them. This is sometimes called "Imputed Righteousness" but is really nothing more than Gnostic thought. Christians, in almost every denomination, believe the Torah of Moshe was "that old stuff for Jews but isn't what the New Testament is all about." Christians think prayer and worship are wonderful, but actually doing the physical requirements of Torah -- such as eating kosher or setting aside the Sabbath -- is not important any more. They have, unwittingly, embraced Platonic thought -- that physical activities are less important than so called spiritual activites. Not only is this at complete odds with Hebraic Thought and thus Scirptural Thought -- but it is nothing more than Gnosticism reborn.
With the intense amount of anti-semitism which has invaded the "church world" since the early 4th century, it is no wonder that Hebraic Thought has been rejected in favor of Greco-Roman pagan philosophy.