My thesis is that Adam was bound to fall. How long Adam or Eve could resist not eating the forbidden fruit? Because as long as Adam and Eve were in the garden that tree was always before them. As long as they resist eating the fruit they would remain in the garden. The tree was a constant temptation. Suppose they withstood the temptaion, then as per God's blessing they would have children. Then the problem would have multiplied because it was possible that not the parents but children would fall for the fruit. In any case sin would have entered in the garden.
It is fairly easy to see the ramification of events after the fact. We do know that God was expecting man to fall since He told us that He planned mankind's salvation before He created the world. "Knowing that you were not redeemed with corruptible things, like silver or gold, from your aimless conduct received by tradition from your fathers, but with the precious blood of Christ, as of a lamb without blemish and without spot. He indeed was foreordained before the foundation of the world, but was manifest in these last times for you who through Him believe in God, who raised Him from the dead and gave Him glory, so that your faith and hope are in God" (I Peter 1:18-21).
That the tree was a constant temptation is not supported in the text. Take note of the description of the garden: "The LORD God planted a garden eastward in Eden, and there He put the man whom He had formed. And out of the ground the LORD God made every tree grow that is pleasant to the sight and good for food. The tree of life was also in the midst of the garden, and the tree of the knowledge of good and evil" (Genesis 2:8-9). How many species of trees does this world contain which are either pleasant to see or good for food? Then add that it is possible that since the days of the flood we might have lost a few varities. Obviously, from the description the garden in Eden was not a small place.
Notice as well that the forbidden tree was placed in the middle of the garden where a person had to go by many other alternatives before reaching it. God gave mankind choice, but He did not place a constant temptation in front of them. The Bible tells us that such is against God's nature. "Let no one say when he is tempted, "I am tempted by God"; for God cannot be tempted by evil, nor does He Himself tempt anyone" (James 1:13). God allowed men a choice, but He designed it so man did not have to sin or even desire to sin. "No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it" (I Corinthians 10:13).
The problem is that Satan wants us to fail and makes sure we notice things that would best left unnoticed. He creates situations to make what is harmful seem appealing. He is limited in what he may do, but his impact is seen throughout the world. That is what Satan did to Eve; he pulled her attention toward what was forbidden, fanning her own desires, which ultimately led to her downfall (Genesis 3:1-8).