Itachi's epistemology (and why I think it's such a clever choice)
During the buildup to the fight between the Uchiha brothers, Itachi says something which stuck with me, probably because I study philosophy and it was overtly philosophical but that's neither here nor there.
Itachi's words are as follows: "Each of us lives, dependent and bound by our individual knowledge and our awareness...All that, is what we call reality...However, both knowledge and awareness are equivocal..Ones reality might be another's illusion, we all live inside our own fantasies."
I just think this is such a fantastic character choice because it's using Itachi's view on perception, and thus knowledge in order to tell us about his character.
Given that he thinks perception is a good source of knowledge we can roughly infer that he is some sort of empiricist, we are able to gain knowledge about the world by experiencing it using the five senses is one way of wording such a view.
Another implication of this quote is that we can ONLY gain any worthwhile knowledge from these experiences, and this all culminates in an understanding of the universe which is then called reality.
Now the thing that really interests me is that he seems to be some sort of anti-realist about truth, talking about how each individual has their own reality constructed from their individual experiences.
This is such a clever choice for his character because Itachi's whole gimmick is that he's a master of illusion and genjutsu, and especially with his signature technique Tsukuyomi, which does the work of constructing the sense data which constructs reality, and so, sceptic that he is, he understands fully that it is entirely possible that he too is under a similar technique and is just none the wiser (a glaringly obvious Descartes reference if there ever was one). I think this is such a lovely bit of characterisation because of course such a talented illusionist would take such a radically sceptical view of things, and how he would come to distrust his own senses and reality as he toys with the reality of others through his technique.
But the the opposite of what he does, isn't it?
He isn't empiricist - he outright mocks viewing world by what you experience alone, because that's how manipulations and propaganda works. That's how he constructs the perfect fantasy Sasuke is supposed to live in and it's only knowledge he's never supposed to actually gain that would tell him the full story.
For me Itachi is cynical. He doesn't defend the system because he thinks it's good - he sees exactly how broken and rotten he is, he just doesn't see a better alternative. All he sees beside it is war. Uchiha might see their coup as righteous revenge for years of oppression, but villagers will see it as violence destroying their peaceful lives - and both sides are right. Both live their own 'reality'.
Your life is what you imagine and your most unshakeable truths might be lies to them. That's what Itachi's entire life as been about: spying for his clan while snitch to the Leaf, plotting against the clan while pretending to work for them, fulfilling Leaf's genocide order while using it to spare Sasuke's life - and finally spend every moment of his life to create complete life for Sasuke to live in, one where he was a monster for Sasuke to defeat and become a hero to settle back into village he was never supposed to learn was build on skeletons of their own family.
Also, apologies for going on a tangent here, but Itachi isn't just a sceptic, and he isn't merely paranoid about a potential pseudo-Tsukuyomi falsifying his perception. Based on his dialogue as an Edo Tensei (and narration from the novels), Itachi believes that he closed his eyes to viable alternatives in the lead-up to the massacre. His perception of reality is flawed, even without genjutsu involved. So, alternatively, that line could also be interpreted as an expression of Itachi's hidden regrets and uncertainty.
