In the famous TOS episode "Mirror, Mirror", we see Uhura, Kirk, Scotty & McCoy transported to the mirror universe. If this was a true mirror universe, then why would Spock be logical and not purely emotional? All the other characters seem to be the reverse of themselves except for Spock's logic as far as I can tell.

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    Rom had similar issues with that universe
    – Izkata
    Commented Apr 3, 2014 at 4:29
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    In James Blish's printed adaptation of this episode (based on early scripts rather than having actually seen the show), Spock says something to the effect of "Doctor, I am a barbarian, in either universe. But some day, I hope to outgrow it."
    – keshlam
    Commented Apr 3, 2014 at 12:37
  • The Halkans were pretty much the same (idealistic pacifists) in both universes. Commented Apr 3, 2014 at 18:49
  • Is there any canon proof that mirror universe characters are not mirrored by nurture rather than nature? Commented Apr 1, 2018 at 23:55
  • There are invariants between the two Universes. I have been looking for a clip where "our" McCoy observes that there is the same acid burn on his table as in "our" Universe.
    – releseabe
    Commented Jun 22, 2022 at 18:20

4 Answers 4


It's just an alternate universe. The "Mirror" universe is just a name, based on the title of the original episode. The Point of Departure (PoD) is when Zefram Cochrane murdered the Vulcan who made first contact with Earth, leading the humans to steal the ship and subjugate Vulcan en route to creating the Terran Empire. As such, the Vulcans were still logical beings, merely subjects of the TE rather than citizens of the Federation. That Spock eventually rose to rule the Terran Empire is likely based on his half-human heritage.

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    That makes so much sense! Commented Apr 3, 2014 at 4:42
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    That's not necessarily the Point of Departure. The opening credits in ENT: In a Mirror, Darkly, replace footage from our universe's moon-landing with footage of an astronaut placing a mirror-universe-Earth (Earth with sword) on the moon, so something seems to be have been different already then. Commented Apr 3, 2014 at 10:07
  • I had forgotten that credits scene, to be honest. Cochrane's actions are what made the Terran Empire a space-faring one, though Earth's culture was obviously more violent and warlike before then. Commented Apr 3, 2014 at 11:14
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    @O.R.Mapper Comments by alternate-Hoshi indicate the split was at least as far back as Shakespeare
    – Izkata
    Commented Apr 3, 2014 at 11:35
  • @Izkata: Interesting - do you happen to have a source/quotation? Commented Apr 3, 2014 at 11:59

The Mirror Universe's Earth was even more barbaric than our Earth. Human nature was less kind. This was reflected throughout the history of Mirror Earth. Recall that in one of the episodes, one of Shakespeare's works viewed barbarism in a good light.

"Mirror" is a loosely used term. Not everyone or thing was exactly the opposite of our universe. Vulcans were still logical. Their history was affected by meeting humans.

  • I think some assume that people in the past had similar morality to moderns. I asked a history professor whether Rome needed justification for their conquests and he said something like, they did not need them. I later read that they thought mercy "soft." So something like a Terran Empire seems plausible -- and what would nazis have done with space? Pretty much what is shown in ST, I thinks.
    – releseabe
    Commented Jun 23, 2022 at 18:50

The true mirror between the "prime" universe and the "mirror" universe isn't a physical inversion. If it were, you might expect to see Kirk as a female comm officer and Uhura as a male captain. Perhaps the Enterprise would be a seafaring vessel rather than a spacefaring one.

Instead, the true surprise and shock of the crossovers come not from the physical nature of the opposing universe but by the inversion of its moral impetus. When characters on either side meet one another, they are not horrified by how unrecognizable their counterparts are, but by how recognizable they are and the resulting discord that comes of their terrible actions. The characters don't want to be faced with the appalling nature of the person they could have become, had they been born into the wrong universe.

Outside the canon, it's also a mirror of the rest of Star Trek as a whole; While most "standard" episodes of the entire Star Trek franchise go out of the way to show humanity as we could be in our best possible future, the "mirror" episodes subvert that and show humanity as we could be in our worst possible future. Instead of a hopeful bellwether, it's a dire warning, especially as we get into

the Terran empire's fall and subjugation of humanity by the Cardassian/Klingon alliance.


Let's compare the universes.

In both, J. Kirk was a competent leader, Spock a science officer, M. Scott an Engineer, H. Sulu a helmsman with a thing for Uhura, Uhura a communications officer. It's clear their aptitudes are much the same, even as their tolerance for both violence and the use of force are not.

Looking at the DS9 mirror episodes, likewise: The basic aptitudes remain, and many but not all the personalities are recognizable. The propensity to use sex and violence to accomplish goals is again higher, and we see more clearly that selfishness is higher, but, really, the basic personality is close. Especially close parallels are Garrik, Bashir and O'Brien; the least close are Kira and Sisko - and yet, some elements are still present. Kira remains a sesualist - in the prime universe, she's constantly fighting it, while in the mirror, she's reveling in it; likewise, she's a practical rules-give-way-to-needs kind of leader in both. Sisko, in the mirror, is still a ship driver - but isn't a military officer in the mirror, and so has a considerably different skill set.

So, for Spock, and Vulcans in general, Logic as a means of preventing their own self-destruction is almost a requisite. They are not the pacifists of the Prime universe, but are still capable of logic, and have the same aptitude for logic. Therefore, Mirror Spock is quite likely to be using logic, as he's a knack for it, and for sophistry as well, just as Prime Spock does, and Alternate Timeline Spock, as well. All have the aptitudes to science, to logic, and to tolerating human coworkers. The Mirror Spock is willing to use force when appropriate for his Empire, just as Prime Spock is willing to do, save for the higher bar before it is acceptable. Alternate Timeline Spock is somewhere between the two in terms of use of force, but also is less logical, thanks to certain personal losses.

We see that Spock is actually possessed of a high aptitude for logic - As a Kohlinaru, he's pushed well past the point most Vulcans even desire, and to a point where he's recognized for his logic. And, while he forgoes the title, he's still extremely logical in both the prime and as old Spock in the Alternate. Logic is inherently something all three Spocks are good at.

Bottom line: Logic is both a skill and a reflection of an Aptitude - Spock has an aptitude for logic, both as a Vulcan and an individual.

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