Memento Mori

Memento Mori has many meanings, but in the vaguest, most literal sense it means: "remember (that you have) to die". Many philosophers argued that there was no point in philosophizing anything if it did not focus on the concept of mortality or death; because if there was one thing that we were all equal in, if there is one thing that unified us as humans: It was death. " The expression emphasized Heaven, Hell, and the salvation of the soul in the Afterlife. 

Remember, Decim kept the dummies from his visitors and dressed them up as they were in their lives so that he could have some remembrance of them before he lost his memories (before his memories were erased, because that is what happens to arbiters--He can only 'live in the moment', he cannot remember the past because that would 'cloud his judgement'. Perhaps Occulus did this as a statement, as if to say "Humans make bad choices because of their memories and their fears associated with those memories; so if arbiters are to be effective, they can't have memories." -- Though Nona would probably argue that "Without emotions, humans can't be judged properly, because they do make their decisions based on their memories and their emotions associated with them; and without emotions, we can't judge them properly." That is also what Decim began to say when he described his most ideal way to judge humans, because he "respected their lives"). And these dummies are no longer tangible, physical beings any longer; they are only a fleeting memory of people who are still living, or in this case, dummies without context in Decim's bar. This could also be a literal metaphor that we are all simply souls in a dummy body that we leave behind when we die. 

It is what a person does now (during judgement), however, that matters (in life: 'now' being 'how you choose to live your life' either by sinning or choosing to live more respectfully -- in the anime: this is how they are judged, in the moment, testing them by giving them hardships in the game in order to see their darker sides). Chiyuki passed this test in the last episode when she wanted so badly to live but could not push the button (do wrong to someone else) because 'she knew' that someone else would die and someone else's parent, sibling, or friend would be very sad to lose them. The hardship here was Chiyuki's desire to live, but she didn't give in to that dark side-- Until she did, at which point Decim lost it and could not maintain the scene of the judgement. 

Towards the end Nona was attempting to change the way humans are judged, attempting to make Decim as close to a human as possible so that he could judge them properly: Because as Chiyuki said, humans are not that simple. Towards the end Decim began to grasp that concept, and could not deceive Chiyuki like he was supposed to.

There were two opposing views on the arbiters in the anime: According to Occulus, which he pretty much blatantly said: Arbiters do not experience death, so therefor they are ' not living'.  Nona had a far different view: That they did not die, but they 'lived in the present'. The two of them never seemed to come into an agreement, and this could be viewed as two ways to look at life: One, you can view life as something strictly organic, something that comes and passes; or, you can look at life as something that exists in the moment, as strictly the soul.  Perhaps Occulus was trying to imply that the visitors were nothing more than souls in a dummy body, and so they are 'not currently living' and therefor they should be judged by arbiters whom are also 'not living'. Obviously Nona's view is the exact opposite.

It was also interesting that Memento Mori was revealed to be the name of the drink that Decim had Chiyuki drink (nearly) every time he made a drink for her: The moment that he revealed the name of the drink should have been the most clear and obvious foreshadowing moment in the anime, and yet it seems like it passed by all of us without being interpreted as ' remember chiyuki, that you have to die'. I don't know about you, but I feel pretty stupid for not noticing all the little bits of foreshadowing given to us throughout the anime! That being said, this anime was wonderful. It does not disappoint. It might make you cry though. I did!