Captain Kirk’s reputation for disregarding Federation principles has become an affectionate joke among Star Trek fans. Numerous episodes in The Original Series involved active interference in planetary cultures that he considered behind. Nowhere was this more apparent than The Original Series Season 2, Episode 5, “The Apple,” which hinged on Kirk’s seemingly flagrant violation of the Prime Directive. The episode makes an overt reference to Paradise Lost, and it concludes with Spock actively comparing Kirk to Satan in that story. He backs off of the claim, but the analogy is correct: Kirk brings knowledge at the expense of bliss, which encapsulates not only the episode’s connection to Paradise Lost but the franchise's larger moral puzzle over the Prime Directive.

The episode involves a beautiful world that closely resembles Eden, whose inhabitants live blissful lives untroubled by labor or conflict. Their benefactor is an advanced machine called Vaal, which can manipulate the weather and other elements of the planet’s ecosystem at will. It holds the Enterprise in its grip until Kirk arranges for the ship’s phasers to overload it. Destroying Vaal means that the planet’s inhabitants will need to care for themselves going forward.

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Throughout the episode, Spock maintains that Kirk’s course of action violates the Prime Directive: Starfleet’s rule against noninterference with the normal evolutionary advancement of any species not yet capable of warp drive. Kirk overrides him with the justification that the planet's society is stagnant and therefore cannot evolve normally. It’s a less-than-sturdy argument, but Kirk made it more than once during The Original Series: notably Season 1, Episode 21, “Return of the Archons,” which entailed another godlike machine controlling a perfectly ordered society.

Regardless of the veracity of his claim, Spock remains unmoved. He goes along with his superior officer but ends the episode repeating his claims that he believes their actions violated Starfleet protocol. He then goes on to make the Paradise Lost comparison. The notion not only explains the episode’s title -- a reference to the Tree of Knowledge's fruit, which Adam and Eve eat after Satan tempts them -- but also turns into a sly dig at Spock’s own infernal appearance, as Kirk playfully turns the rhetorical tables on him and suggests that his Vulcan first officer is the real "devil."

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Yet, Spock's comparison is quite apt: not in terms of Kirk being evil, but in terms of Satan’s role in the myth. The serpent disrupts paradise, but he brings knowledge with him. Through learning, Adam and Eve grow, developing the skills to survive in a harsher world only after being denied the pleasures of having everything taken care of for them. Far from being sinister, the reference is a sly way of suggesting that Kirk is precisely that kind of Satan figure in the drama that has just taken place.

And indeed, Paradise Lost fully bears out Spock’s analogy. In the book, before he fell from God’s grace, Satan was known as Lucifer: the bringer of light and knowledge rather than evil. That’s very much in keeping with Star Trek’s message of science and learning as keys to enlightenment, adding another layer between the two characters’ exchange. Spock certainly would have known the double meaning when he made the reference, which indicates of how carefully “The Apple” makes its primary point.

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