The Rule of Two was developed as a way for the Sith Order to

  1. Survive

  2. Weed out the weak

The whole mechanic of the Apprentice killing the Master allows for only the strongest to survive and advance the order. That reminds me of Natural Selection and made me wonder if Lucas based it on that.

  • 2
    I don't see how this has anything to do at all with Natural Selection at all. Natural Selection is about survival and adaptation in particular environments within particular niches. The Sith order is about power and ambition. I'd say you have a far better chance of survival if you aren't part of the Sith Order, what with them killing each other all the time. A bird is going to overpower a moth every day of the week, but moth's still exist and thrive. Mar 18 '16 at 13:04
  • @GorchestopherH Actually Natural Selection is about the survival of the species as a whole not the survival of the individual so in that sense the rule of two is very similar to Natural Selection. Mar 18 '16 at 19:46
  • The only part that even remotely parallels natural selection is that the rule of two is for survival. In general, it seems to be an extremely poor comparison. The only thing keeping me from downvoting is the fact that doing so seems to attract more upvotes. Mar 19 '16 at 19:13

Probably not.

The Rule of Two served two functions:

  1. Stop infighting amongst many Sith vying for power. With only two Sith, they had to work together.
  2. Strengthen the Sith Master over time, since each Master would be defeated by his successor and thus the succeeding Master was theoretically stronger for having defeated his predecessor.

The first and primary function is articulated well on Darth Bane's (archived) page from starwars.com:

An ancient and legendary Sith Lord, it was Darth Bane who saw that the Sith traditions of old were ultimately a dead end. All too often, squabbling Sith in their bid for power upended carefully laid plans and planted the seeds of their own defeat. After the Sith were decimated by the Jedi Knights of a thousand years ago, Bane enacted the Sith rule of two: there would be only two active Sith at one time -- a Dark Lord to embody the power, and an apprentice to crave it.

The second function is obvious from the nature of the Rule of Two, but is best articulated in Legends:

Under [Bane's] leadership the Sith had been reborn. Now they numbered only two—one Master and one apprentice; one to embody the power of the dark side, the other to crave it. Thus would the Sith line always flow from the strongest, the one most worthy. Bane’s Rule of Two ensured that the power of both Master and apprentice would grow from generation to generation until the Sith were finally able to exterminate the Jedi and usher in a new galactic age.

Dynasty of Evil, p. 9 (Legends novel)

It's true that the second function sounds vaguely like natural selection. For example, Encyclopaedia Britannica says that

In natural selection, those variations in the genotype that increase an organism’s chances of survival and procreation are preserved and multiplied from generation to generation at the expense of less advantageous ones.

However, the second function follows from the first: the Rule of Two was instituted to stop infighting, and the practice of the apprentice killing the Master was mostly a consequence of the drastic reduction in the numbers of the Sith. The first/primary function doesn't have anything to do with natural selection, so it doesn't look like the Rule of Two was based on natural selection.

Furthermore, the Sith Order's behavior prior to the Rule of Two arguably looked like natural selection as well -- some Sith were "selected" by the Force to be stronger, and these stronger Sith were able to kill off the weaker ones. And there's no reason why a Sith Order composed of many Sith Lords couldn't institute a rule that each Sith apprentice must kill his Master so as to strengthen each Sith from "generation to generation".

Lastly, I can find no mention of natural selection in the context of the Rule of Two in any Star Wars source (various novels about the Sith, Wookieepedia, starwars.com, etc.).

  • Good answer, but if you want a source which is pretty clearly still part of the new Disney canon rather than the old starwars.com page whose canonical status is less clear, there's a good explanation of the origin of the rule of two on pages 138-139 of The Phantom Menace novelization (which also predates that starwars.com page), available on google books here. Page 4 of this interview with George Lucas also shows his thinking in devising the rule.
    – Hypnosifl
    Mar 18 '16 at 15:16
  • @Hypnosifl Those are great finds. I think you should put them in an answer of your own so you'll get credit for them. I'd upvote such an answer.
    – Null
    Mar 18 '16 at 15:23

No, it wasn't really about strengthening the Sith through natural selection. The basic rationale for the rule of two was that the Sith tend to struggle for power with each other, which had led to a disaster where nearly all had been killed, so with only two they could spend most of their time plotting against the Jedi instead of infighting. A master/apprentice relationship is more stable because the apprentice will for many years avoid trying to kill the master since the apprentice still has more to learn, and the master wants to have an apprentice to continue the Sith plot against the Jedi if the master should die for some other reason, such as old age (the master also presumably enjoys having a powerful flunky to do their bidding, and is confident enough in their greater abilities to keep them safe if the apprentice should ever rebel).

The first in-universe explanation of the origin and rationale for the rule of two was given in Terry Brooks' novelization of The Phantom Menace, on pages 138-139 which are available on google books here:

The rogue Jedi who had founded the Sith order was its nominal leader, but his ambition excluded any sharing of power. His disciples began to conspire against him and each other almost from the beginning, so that the war they instigated was as much with each other as with the Jedi.

In the end, the Sith destroyed themselves. They destroyed their leader first, then each other. What few survived the initial bloodbath were quickly dispatched by watchful Jedi. In a matter of only weeks, all of them died.

All but one.


It was patience that had saved the Sith order in the end. It was patience that would give them their victory now over the Jedi.

The Sith who had survived when all his fellows had died had understood that. He had adopted patience as a virtue when others had forsaken it. He had adopted cunning, stealth, and subterfuge as the foundation of his way—old Jedi virtues the others had disdained. He stood aside while the Sith tore at each other like kriks and were destroyed. When the carnage was complete, he went into hiding, biding his time, waiting for his chance.

When it was believed all of the Sith were destroyed, he emerged from his concealment. At first he worked alone, but he was growing old and he was the last of his kind. Eventually, he went out in search of an apprentice. Finding one, he trained him to be a Master in his turn, then to find his own apprentice, and so on to carry on their work. But there would only be two at any one time. There would be no repetition of the mistakes of the old order, no struggle between Siths warring for power within the cult. Their common enemy was the Jedi, not each other. It was for their war with the Jedi they must save themselves.

The Sith who reinvented the order called himself Darth Bane.

Also, page 4 of this interview with George Lucas from 1999 (the year The Phantom Menace came out) includes a comment where he explains the reason only two Sith can ever stably exist, again because of their tendency towards infighting and struggle for power:

One of the themes throughout the films is that the Sith lords, when they started out thousands of years ago, embraced the dark side. They were greedy and self-centered and they all wanted to take over, so they killed each other. Eventually, there was only one left, and that one took on an apprentice. And for thousands of years, the master would teach the apprentice, the master would die, the apprentice would then teach another apprentice, become the master, and so on. But there could never be any more than two of them, because if there were, they would try to get rid of the leader, which is exactly what Vader was trying to do, and that's exactly what the Emperor was trying to do. The Emperor was trying to get rid of Vader, and Vader was trying to get rid of the Emperor. And that is the antithesis of a symbiotic relationship, in which if you do that, you become cancer, and you eventually kill the host, and everything dies.

  • Good answer but the quote from Lucas seems nonsensical.
    – Kosmos
    Mar 18 '16 at 16:37
  • @Kosmos - How so? The whole thing, or just the last part about cancer vs. symbiotic relationships?
    – Hypnosifl
    Mar 18 '16 at 17:20
  • 1
    How do the Sith even know that there are no other Sith around to break the Rule of Two? If the Sith were so self centered, why take on any apprentices? Why can't one apprentice just as easily poison the master's tea and take over? Why can't a master play off several apprentices against each other so they can't unite against them? Nasty totalitarian states have managed to get lots of bad people pointed in more or less the same direction without having to kill them all first.
    – Oldcat
    Mar 18 '16 at 18:44
  • @Oldcat - You would presumably have to look to the EU to figure out how Darth Bane could've been confident he was the only surviving Sith, but if you take that for granted, it's hard to see how any additional Sith could have arisen outside of Bane's "lineage". As for tea, probably Sith are smart/paranoid enough to keep careful track of where their nourishment comes from? And I don't know that Sith are purely selfish, maybe they can have some "loyalty" to a cause which will outlast their lifetimes if it's rooted in negative dark side type emotions, like their hatred of the Jedi.
    – Hypnosifl
    Mar 18 '16 at 19:29
  • @Hypnosifl He seems to be saying that, under the rule of 2, an apprentice would not try to usurp/kill his master in the way Vader did. As if the apprentice would not try to kill his master by himself. Also yeah, the last sentence is just a bunch of words.
    – Kosmos
    Mar 18 '16 at 19:49

I don't know about Lucas's idea himself, but it's very probable that it's based on natural selection, although it could also be so there's no power vacuum when the apprentice kills the master, if there were more there would be more chaos, the sith want control, so it makes sense that it would be only two

  • 1
    As GorchestopherH pointed out below the question, the OP has misinterpreted the theory of natural selection. So why do you think it is "very probable"? I didn't downvote you, but the person who did is probably seeking more explanation, with references to specific events from the films.
    – Praxis
    Mar 18 '16 at 13:47
  • Very probably because the old is replaced by the new, the older master is killed by the younger more able apprentice, who then trains his apprentice, natural selection in a way, the apprentice is stronger, and the films don't really go into the rule of two that much, it's the comics and other fluff material that goes into it in detail and o have a loose grasp on those
    – Edjm95
    Mar 18 '16 at 14:44
  • 1
    @Edjm95 I didn't downvote you either, but someone old being replaced by someone stronger and more able has nothing to do with natural selection at all, it doesn't even vaguely imitate it. Birds that eat certain bugs thriving when their physical features favor the eating of that bug has nothing to do with lust for power and dominance. There is almost no similarity at all. Mar 18 '16 at 15:21
  • I'm not sure how you can draw a conclusion as very probable when there's literally nothing in text that relates to the theory at all. What if I fabricated a theory that Yoda was created and based from a troll doll because George Lucas had an affinity for them. There's no evidence for this, but since it's entirely plausible, using your logic it's very probable.
    – John Bell
    Mar 18 '16 at 15:21
  • 1
    Ah sorry you feel that way. We're not intentionally grinding your gears. The site is geared towards providing accurate, factual information to questions. when you answer a question here, you leave your statement open for interpretation and critique. It's nothing personal.
    – John Bell
    Mar 18 '16 at 15:27

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