As is noted in the Likutei Torah of the Ari, Adam, being a sublime creature, walked in the Upper Mansions and lived in the celestial spheres.
And according to Rashbi, even the greatest human beings in history are not of that stature.
At best they may be able to see something of the upper worlds and make spiritual contact, but they don't "walk about" in them.
Adam, walking freely, did not even bother to cast a glance at the lower worlds of uncleanness.
The serpent, however, enticed him: "Take a look! There are other mansions, another place that you have not visited."
So Adam faltered and, without intending to do so, "fell" into sin.
This is a slightly different version of the Bible narrative.
Its description of the primordial state is more abstract, more spiritual.
However, the essential factors remain: that at first Adam did not even look at these other realities, and that when he did, he could not separate himself.
The only way man could avoid being involved in evil was to remain ignorant of it.
At this point let us make a slight digression and consider the character of Joseph in the Bible.
The selling of Joseph by his brothers is followed by the account of Judah's journey to Adullam, where he took a woman to wife, had sons by her, and then after some grievous mishaps was seduced by his daughter-in-law, Tamar.
This account is followed by the story of Joseph's service in the house of Potiphar and his repulsing the seductions of Potiphar's wife.
There seems to be some message in the opposite ways taken by Judah and Joseph–the way of plunging into the world and its evils, and the way of purity, disavowing the evil of the world.
Each has his own task to perform.
And in the longer sequence of history, they are expressed in the two Messiahs that appear at the end of time: Messiah, son of Joseph, and Messiah, son of David (or Judah).
A similar logic seems to accompany the story of David and Jonathan, son of Saul.
Why was the kingdom taken from the house of Saul and given to David?
Saul was in some respects a very saintly man.
His son Jonathan was certainly a pure soul as well as a brave and perfect human being, while David had more than one side to him that succumbed to temptation.
Can one conclude that too much perfection is unproductive?
Is it necessary for man to "leave his brothers and turn aside to a certain Adullamite" (a stranger), to get so involved with the imperfections and unpredictable dangers of life that almost anything is liable to happen?
According to the Bible, it would appear that there has to be a plunging into the fierce struggles of the world, a confrontation with good and evil.
Even Joseph, who could not be a completely innocent soul like his brother Benjamin, had to go down to Egypt and there perform the act of Tikun, of restitution.
Hence Adam was sent forth from Eden.
The only way to overcome the uncleanness and evil of the world was to go "down" into it and engage in constant struggle.
–Rabbi Adin Steinsaltz
From In the Beginning, "Banishment from Eden," p. 85, by Rabbi Adin Steinsaltz