The first phrase follows from the last phrase of the previous verse, “whether they be unto salvation or unto destruction.” The dualism of salvation/destruction is transmuted into the dualism of good/evil. Taking one pair, Alma extends his meaning with a related and corresponding opposite pair. Thus, salvation or destruction come upon all people, and all men have both good and evil placed before them. Since Yahweh’s decrees are unalterable (v. 4), Alma now needs to show how the unalterable decrees apply to humankind who have options of both good and evil.
Alma notes that “he that knoweth not good from evil is blameless.” In other words, the salvation/destruction pairing does not apply to those who are not accountable under the good/evil pairing. Without being able to separate good from evil, they cannot be separated into saved/destroyed categories either. But the person who knows the difference between good and evil is fully subject to the option of salvation/destruction. Such people will receive the reward they select: good, life, and joy or evil, death, and remorse of conscience being the opposite conditions.
Alma’s teaching that “he that knoweth not good from evil is blameless” echoes Lehi’s instructions in 2 Nephi 2:11 that if there is no “opposition” then “all things must be a compound in one. (See commentary accompanying that verse.) Lehi had worked through the same logic that Alma uses here: “And if ye shall say there is no law, ye shall also say there is no sin. If ye shall say there is no sin, ye shall also say there is no righteousness. And if there be no righteousness there be no happiness. And if there be no righteousness nor happiness there be no punishment nor misery… ” (2 Ne. 2:13).
Thus, people who do not know good from evil are blameless because they are unaware of opposition and, hence, are as innocent as Adam and Eve before partaking of the fruit of the tree of knowledge of good and evil. Of course, Alma is aware that everyone has some knowledge of good and evil as a result of the fall, but he is making a theoretical argument, using verbal symbols, not a literal description of reality. He is using hyperbole to limn the extreme position and to make the ramifications of the issue clear. For Alma, once we know the decrees, we are firmly accountable to them.
Knowing the difference between good and evil will lead to salvation only when we actively choose good so that good will be returned to us. This is Paul’s essential lesson in Romans 2:12–13:
For as many as have sinned without law shall also perish without law: and as many as have sinned in the law shall be judged by the law;
(For not the hearers of the law are just before God, but the doers of the law shall be justified.
Here the “law” is the law of Moses by which Jews governed their life. Paul wants Jews to understand that the law per se did not bring salvation; rather, the “do[ing] of the law” did. Similarly, modern Church members may take false comfort in rituals like baptism, attending church meetings, and going to the temple. We may have the law and we may (per Alma) understand the difference between good and evil, but it is what we do with that knowledge that will lead us to life and joy, or death and remorse.