Unless there is a moral authority, who defines good and evil. The Forbidden Tree in the Garden of Eden was to enlighten the first people on what is good and evil. The fruit thereon, contained the knowledge to discern what is right and what is wrong. Free will was dispensed at that moment! Before our forebears ate of the fruit, they were totally innocent. Dispensationalists call this the "dispensation of innocence". After disobeying, the innocence was dispensed of, and mankind entered the "dispensation of the conscience". After sinning for the first time, their conscience convicted them of their sin, and man and woman felt guilt for the first time! They either elected to do good or evil of their own choosing.
The Tree of the Knowledge of Good and Evil, after it's fruit was eaten, established the dichotomy; man now was drawn toward the desires of the flesh, and away from the comfort of the spirit. Ever since, man has had a free moral choice in life, and hence life became a dichotomy: Our spirit is willing but the flesh is weak. (Matt 26:41). The gravity which pulls mankind from good toward evil is temptation. Temptation is as real pushing down on the mind, as is gravity doing the same on the head. In fact, the very concept of temptation is serious, or having gravity.
Whereas, gravity is an unseen force pushing our bodies toward the world, temptation is gravity pushing our flesh toward the things of the world. Our conscience is the mediator for temptation. Shall we do good or shall we do evil? Discerning people realize that what is evil is destructive, but often do it anyway. Discerning people also know what is good, but elect destruction anyhow for the pleasure of it.
Temptation is the promise of pleasure, and conviction is the recognition that the pleasure is not worth the penalty, Thus, almost every moment, the conscience of most people is a dichotomy between good and evil.
Much of the world recognizes a Supreme Being which Christians and Jews realize is God. As such, "good" and "evil" are defined by God. Only God is "good" (Mark 10:18). The relationship between good and evil is the same as between light and dark.
Luke 11:35 "Take heed therefore that the light which is in thee be not darkness."Darkness is the absence of light, and evil is the absence of good. That describes another dichotomy: Shall we live in light or in darkness. Well, truth is the light and deception is the darkness.
God is good, and God is truth. Hence, "good" is whatever God declares, and what he declares is ultimate truth. Then those who do God's will, endeavor to do "good", and their motivation is truth. God made a covenant with man: Trust me and you shall be saved. Trusting is reliance on the truth. We chose the light half of the dichotomy over the darkness.
With two choices, and only two, what is our motive for selecting one component of the dichotomy over the other. We have a motive. One motive is pleasure, and the other is salvation. Christians forgo pleasure and seek salvation because their motive is ultimate pleasure - living forever. That is one thing Satan never promised with pleasure, but he did imply that with "Ye shall not surely die." (Genesis 3:4). Our motive for trusting Jesus is that we won't die. Our motive for trusting Satan with his temptation is that we are betting that if we sin, we won't die.
My motive in life is to trust in Jesus so that I can live forever. That creates another dichotomy: Am I living for Jesus or for me? The former is goodness and the latter evil. To be saved, it's got to be much more than getting my lousy soul saved. It must be about loving God for saving it. This latter point must be the motive for salvation! It's got to be about Jesus, and it can't be all about me.