I haven’t seen most Star Trek episodes since I was a young teen, so I tried rewatching this one, you know, with the alternate universe and the evil Spock. It was good!
I took away from it the main lesson that our moral behavior — or lack thereof — is one of the most contingent and fragile features of our universe. The possibly happy ending for the bad universe drives this point home, as does the opening speech from the indigenous folk (the Halkans) who won’t sell their dilithium crystals, reminding Kirk that the Federation too might turn bad. Add to that the utter implausibility of their “highly moral” behavior in the bad universe, as the absurdity and unlikelihood of their invited destruction reminds us that virtually everyone is pliable in response to strong enough incentives.
If you think through the plot, to the extent the “good” people are more powerful and effective than the “bad” people, that is because the “good” people are better at deceit. Though the good people can teach deceit to the bad people, as the good Kirk does at the end to the evil Spock, who perhaps will reform. Another embedded lesson is that both the “good” and the “bad” men will sexually harass (both the good and bad) women, with the major differences being those of style not substance. And the “good” men seem to prefer the “bad” women.
If the “bad” universe were safer, would the powerful people find it better or worse to live in? What if you had a Ring of Gyges to help you along?
Overall you can read the whole episode as “the spirits” (God?) sending a Shakespearean-like dream to Kirk, so that he can better understand the perspective of the Halkans, which otherwise he finds baffling. Might the Halkans have sent the dream themselves?
Recommended, it was better and more idea-rich than expected. I will try another episode soon.