I've long been fascinated by the isekai prospect of reincarnation, or rather, the impossibility of it happening as it is often depicted. Biology would tell you: if you're talking about teleporting/summoning someone to another world, there are a lot of issues that anime never covers. A quick look into history (the ages of conquest and exploration) shows that disease quickly becomes an issue when a foreigner treads into an unknown land. Anime completely ignores the fact that any person who lives on Earth and is then transported to another world would have to deal with a myriad of diseases, parasites, viruses, and bacteria that we do not have any resistance to or immunity to. Comparably, our companions in that new world aren't impervious to the maladies we carry. That said, Mushoku Tensei presents a neat little solution to these woes, being re-born there. In utero, a mother's antibodies are passed on to the child, thus preparing that individual for all the ailments their world possesses. But in that approach lies another conundrum, that of nature and nurture, or rather how both these things affect a person’s outlook on life.
Our day-to-day interactions are significantly influenced by the individuals who surround us. Every time we engage in undesirable behavior, we are admonished for it, through that, we gain an understanding that our behavior is either acceptable or unacceptable. Similarly, our perception of what’s right ages as we do, thus prompting us to adjust and assimilate to expected social standards. And here is where Mushoku Tensei shines: honest character building. Rather than a blank slate, Rudy, for most of his past life was a hikikomori, and this affects his new life far more than he (and even we as viewers) realize. The acquisition of social cues is attained through learned behaviors. Behaviors that must be frequently exercised in order to maintain their effective execution. In the case of an individual such as Rudy, who endures a plethora of adverse encounters and subsequently withdraws from society, the faculties of empathy and social perspicacity are profoundly insufficient. What appears overtly intuitive for most individuals can easily be missed by someone in Rudy’s position.
This lack of social awareness and expected morality is further exacerbated in his newfound life, due to growing up in the Greyrat household and in the Six-Faced World as a whole. Rudeus throws himself headfirst into living out his new life and voraciously learns about the world around him. Through this he garners an appreciation about the norms of his new world. He sees first hand how things like Paul's predatory behaviors is often disregarded and even downplayed or just accepted by those around him. Faced with these lessons, it make it easy for Rudy to ease into a less-than-ideal moral lifestyle because he has some assurance that he has a lot of leeway with his behavior, leeway he would never have had while living in Japan. However, it's not just learned behavior; there is a level of societal understanding due to his prior life
There is a philosophical concept known as "Chesterton's Fence." Which postulates that when faced with a problem, before rushing towards what seems like the easiest solution, it is prudent to assume that an existing arrangement is the way it is because an individual(s) who established it has presumably given thought to potential alternatives. The example used here is that you should never remove a fence, no matter how bad it is or how much it annoys you because you don't understand the full implications of why that fence is there and what happens if you remove that fence. An easy way to understand this in modernity is the issue of authoritarian leaders. Few people would argue that they needs to remain in power (the fence that needs to be removed). But as the recent Wagner revolt showed, the potential removal of an autocrat isn't as clear-cut. In Russia’s example if Putin is deposed and a civil war breaks out, hundreds, if not thousands, of weapons of mass destruction would fall into the hands of out-of-state actors. Then, instead of dealing with a centralized autocrat, you have to deal with insurgents and extremists; all of who have different goals. That doesn't detract from the fact that having an autocrat in power is a very bad thing; it just poses the possibility that the alternative may be more destructive and harder to deal with.
In Mushoku Tensei, Rudy is smart enough to understand this dilemma. He has a modern understanding of morality (albeit warped). For example, he hesitates to kill, and the time when he can get what he wants through force, he always abstains from going that route. But at the same time, he understands that what applied to his old existence is to a degree, invalid in his present one. His abstention from something, while admirable, serves no purpose but to make his life harder than it already is. He knows that the things that don't confirm with the morals and values of his old world are still present in his new one for a reason even if its a deeply flawed reason. It may still be detestable, but much like heading back into our own history and trying to change problematic issues in a flash, he's cognizant enough that he alone can't bring about meaningful change in his current position.
To a large extent there is also a willing rejection of his old life and values. In the most recent episode, Rudy again runs into Nanahoshi Shizuka. His reaction to this was visceral, an excellent nod to how past physical trauma translates to emotional trauma in the long run. But after that initial shock (and with the help of Fritz), he was able to push aside his feelings and not only face his former aggressor but also work alongside her. It is a feat of emotional maturity most people would not be able to do. While it may not be one he did without hesitation, it is one he knew was inevitable given the circumstances he finds himself in. It is possible to discard deep-seated differences or hatred and work alongside someone you once abhorred once a mutual understanding develops, and the latest episode presented that pretty well. Even in our world, things like WW1's Christmas Truce can happen between people who just hours before were trying to kill each other.
But the most important takeaway from this exchange was Rudy's outright declaration that he does not want to return to his previous life. He has friends and family that he loves and cares for in his present life, whereas he misses nothing of his former one. Nanahoshi mentions that such a disposition signifies a life well-lived, free of remorse in its final moments. While Rudy's previous life did not end the rosy way Nanahoshi believes it did. Compounded, the rejection of his former self, accompanied by the renouncement of his previous existence, presents a profound and revealing window into Rudeus' psyche. That rejection applies not only to the past life he lived but to his past self as well, along with the concepts and ideas that his old life held. He's no longer a nameless shut-in; for all intents and purposes, he is now Rudeus Greyrat, a Six-Faced World native, no different than anyone else in that world. While this may ostracize him to those in line with the norms of his past life, in his current life, being just a normal person is to his benefit.
