Star Trek has done a lot when it comes to representation in film, acting as a platform to tell futuristic allegorical tales that are meant to highlight topical issues. They do this frequently, from exploring the idea of relearning humanity after trauma, to questioning whether holographic or synthetic life has any human (for want of a better word) rights at all. They don’t always get it right — for example, when it comes to the Ferengi. But one such notable moral quandary comes into play in full force during Star Trek: Voyager.
The 24th episode of Season 2, “Tuvix,” is centered around the quagmire of transporter technology, and what happens if individuality and identity are lost as a result of a transporter error. Lieutenant Tuvok (played by Tim Russ, who oddy also starred in Spaceballs) and ship chef and guide Neelix (Ethan Phillips) are gathering materials from an unnamed planet, when, upon return to the ship, the aforementioned transporter error splices their DNA together, merging their bodies and consciousness into one being: Tuvix. The two could not be more different — Tuvok, being a Vulcan, is logic-driven and reserved; Neelix, a Talaxian hybrid, is outgoing, boisterous, and a social butterfly. They have never seen eye to eye ever since being first introduced to one another, making them the perfect victims for the nefarious writers of this episode.
The ethical implications of this character's existence don’t seem too great at first: they are two beings who simply need to be separated to become those characters that both the audience, and others in-universe, have grown to know and love. That would be simple enough if Tuvix were simply an amalgamation of two beings, but he’s not. Rather, he’s a whole new life form with one consciousness — it just so happens to be made up of two beings. If anything, this amalgamation of the two is the best of each person, taking the best and most admirable qualities from both parties. Something that could be done in the blink of an eye by a Q, however, is explained to be near impossible to reverse. Tuvix is able to perform both Tuvok and Neelix's duties perfectly and is having a grand old time doing so. While he’s enjoying his newfound life, the crew are slowly coming to terms with the merge, realizing they might potentially have lost two friends. Tuvix’s mere presence is a haunting reminder that neither Tuvok nor Neelix is really around anymore.
Time goes on, and over the course of a few weeks, Tuvix establishes himself about the ship, forming friendships. However, those closest to Tuvok and Neelix still mourn their "deaths," for want of a better word. Then comes the real crux of the episode, one which brings into question the ethics of individuality and the scarcity of life no matter what form it takes. The Doctor discovers a way to reverse the accident, and the crew rejoices, happy to know that they will get their old friends back. Tuvix, however — completely understandably — is not so happy, and does not want to die. He’s shocked by the reaction of those he thought were his friends, essentially willing to kill him to get their old buddies back without blinking an eye. It has to be said that, while it may be understandable to some degree, the overall possible support of Tuvix’s execution, as that is in essence what it is, seem very out of place for Starfleet.
In a lot of ways, it is a horrible episode to watch, especially as Tuvix grows more and more desperate. He really does not want to die, and cannot get his head around how he could be seen as selfish and the bad guy simply because he wants to keep existing as himself. The Doctor is the only one seemingly able to see this, protesting Janeway's decision to continue with the procedure despite Tuvix’s objections. It makes sense; being a doctor, he is more likely to see and appreciate the value of life, and would never consider taking a life to save another — it goes against everything he stands for.
To be honest, it should go against everything Janeway stands for too (potential war criminal or not), but this does not stop her from continuing the operation by herself, and basically dragging Tuvix to the transporter bay. He protests, because of course he would, but there is still a lot of Vulcan in him and he and sees that resisting is illogical. His last words are:
“Each of you is going to have to live with this, and I'm sorry for that, for you are all good, good people. My colleagues, my friends, I forgive you.”
And that's that. Janway reverses the Transporter merge, and out come Neelix and Tuvok as two separate entities once again. This decision is one reason a lot of fans dislike Janeway, especially when comparing her to someone like Captain Sisko. Janeway does this terrible thing, and after the episode finishes, it is never talked of again. She simply returns to normal, without carrying this huge weight of her actions, whereas someone like Sisko, a far more three-dimensional character (even if the entirety of one of those dimensions is filled with over-dramatic monologues), would carry around this guilt and use it to become a better person.
Identity and individuality are shown in this episode to be quintessential to a person's being, but also that they are fickle. When merged together, they can create a completely different person, much like the Trill symbiont, taking aspects from both, but becoming something new — something that is greater than the sum of its parts.