God has all the attributes of godliness in their perfection. It is not within his nature to do that which is less than godly. He cannot create that which is unwholesome or evil. That which he creates is without corruption or sin of any kind.
Thus it was requisite with the plan of salvation that Adam fall, that he introduce mortality and corruption, that he, through the Fall, create a condition in which men might know opposition and knowingly and deliberately seek God.
Had Adam not partaken of the forbidden fruit, had he not transgressed, had he not introduced death and corruption into a world where it had not existed in any form, had he not thereby imposed upon his posterity both a temporal and a spiritual death, the plan of salvation would have been of none effect.
Had there been no fall, there could be no atonement; and if there were no atonement, there would be no Savior; and if there were no Savior, there could be no plan of salvation.