You are assuming that Adam did not know what is good through God. Adam could have known good but not known what was evil. For example we know what truth is but also what lies are. So this story was really want to be like gods, to be our own judge of what is good and evil. The judges of Isreal were called gods. See Psalm 82
A psalm of Asaph. 1 God rises in the divine council, gives judgment in the midst of the gods.
2
"How long will you judge unjustly and favor the cause of the wicked? Selah
3
Defend the lowly and fatherless; render justice to the afflicted and needy.
4
Rescue the lowly and poor; deliver them from the hand of the wicked."
5
2 The gods neither know nor understand, wandering about in darkness, and all the world's foundations shake.
6
3 I declare: "Gods though you be, offspring of the Most High all of you,
7
Yet like any mortal you shall die; like any prince you shall fall."
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4 Arise, O God, judge the earth, for yours are all the nations.
Footnotes
1 [Psalm 82] As in Psalm 58, the pagan gods are seen as subordinate divine beings to whom Israel's God had delegated oversight of the foreign countries in the beginning (Deut 32:8-9). Now God arises in the heavenly assembly (Psalm 82:1) to rebuke the unjust "gods" (Psalm 82:2-4), who are stripped of divine status and reduced in rank to mortals (Psalm 82:5-7). They are accused of misruling the earth by not upholding the poor. A short prayer for universal justice concludes the psalm (Psalm 82:8).
A psalm of Asaph. 1 God rises in the divine council, gives judgment in the midst of the gods.
2
"How long will you judge unjustly and favor the cause of the wicked? Selah
3
Defend the lowly and fatherless; render justice to the afflicted and needy.
4
Rescue the lowly and poor; deliver them from the hand of the wicked."
5
2 The gods neither know nor understand, wandering about in darkness, and all the world's foundations shake.
6
3 I declare: "Gods though you be, offspring of the Most High all of you,
7
Yet like any mortal you shall die; like any prince you shall fall."
8
4 Arise, O God, judge the earth, for yours are all the nations.
Footnotes
1 [Psalm 82] As in Psalm 58, the pagan gods are seen as subordinate divine beings to whom Israel's God had delegated oversight of the foreign countries in the beginning (Deut 32:8-9). Now God arises in the heavenly assembly (Psalm 82:1) to rebuke the unjust "gods" (Psalm 82:2-4), who are stripped of divine status and reduced in rank to mortals (Psalm 82:5-7). They are accused of misruling the earth by not upholding the poor. A short prayer for universal justice concludes the psalm (Psalm 82:8).