I don't know how many of the people who read my modest blog have played RPGs, but I've played a fair bit of console RPGs my entire life (I just bought Skyrim today and have been playing through Disgaea 4 for the past month lol). In most of these games, there are different classes that you can pick for characters, or your main character, that each have distinctive strengths and weaknesses. For the purpose of this post, I'm going to stick to the archetypes of the thief and wizard.
The thief is fast, has low HP, high dexterity, comes with a myriad of skills that get better as speed and dexterity increase, and all that jazz. The wizard usually is one of the slowest characters, but usually deals the greatest amount of damage among your party. The thief is usually young and energetic, while the wizard is usually old and miserly (i.e. likes to conserve energy).
Many of us like to think that we are the wizard in real life, cognitively. But in reality we are all the thief.
I've touched a bit on System 1 and System 2 thinking. Of course, that is only a short article, Daniel Kahneman has a much longer book devoted to it, which I've also linked to previously.
Like I've pontificated about pretty recently, in order to be a good thinker, one must know how brains think. I don't think I can stress that enough.
In order to be a good guitarist, I had to know how guitars (and the physics of music) worked as well. Without knowing those things, I would only be able to be as good a guitarist as raw ability would have let me. Knowing how the guitar and music in general work increased my aptitude for playing guitar and listening/composing music.
Not saying I'm an awesome guitarist or songwriter or anything, but I'm a lot better than I would have been had I not studied the underlying reasons for what creates good music and how to better manipulate the guitar; how to manipulate the guitar can only be fully realized by knowing how guitars work. There's a significantly high probability that the world's most technical guitar gods all have a deep reservoir of how the guitar physically works.
The same thing applies to thinking, reasoning, and learning. The rough analogy that Kanheman posits is that there are two systems in the brain that we use to reason throughout life. System 1 and System 2. In reality, the two systems are not cleanly delineated into individual systems but for pedagogical reasons that analogy is used. And that's the point; we learn things better by anthropomorphication because anthropomorphication, or having personalities, is like catnip to System 1. And System 1 will readily hand over a thing with agency and personality to System 2, even if that agency or personality is a complete misunderstanding of System 1.
When I would study music theory, I would read things like "The G7 chord wants to resolve to a C chord in a ii-V-I progression". Thinking that a combination of frequencies that are represented by the three letters G B F have a literal personality, want things, and move with intention is nonsensical. But it helps one to remember and learn. There is no Platonic G7 chord "out there" that taps into your auditory neurology and forces this on you. Again this is obviously nonsensical if taken literally, but people seem to apply the figurative personifying language used in other contexts (like love) and think that it is literal. There is no Platonic "love-stuff" out there in space that we tap into when we have feelings for someone anymore than there is "music-stuff" when describing music theory.
Anyway, when reading through the book, I imagine that System 1 is the thief, and System 2 is the wizard. Imagining it like this helps you retain the knowledge faster, and to run with this analogy I'll describe a typical battle encounter when the thief and wizard are roaming the countryside on their mission.
Like I wrote above, we are all the thief. The thief leads the party. When you encounter an enemy, it's the thief who first engages. Either the thief dispatches the enemy herself, or she delegates it to the wizard to take care of it if it is an enemy that the thief can't handle. Of course, it takes a while for the wizard to cast a spell. If another enemy enters the battle while the wizard has already targeted the first enemy, the second (third, fourth, etc.) enemy has to be tackled by the thief... even if she is ill-equipped to kill the enemy.
It's not like the thief sucks, by the way. There are certain things that only the thief can take care of that the wizard would be unable to do. The thief can pick the lock of voice tone over a phone, or steal the secret maps of facial recognition from an enemy. If the wizard tried those things, it would fail spectacularly. The wizard is too slow to pick locks on treasure chests or steal maps from enemies. On the other hand the thief, when she acts, she's preternaturally fast. And the vast majority of the items in your inventory were obtained by the thief, including the wizard's robes and staffs that increase the wizard's spellcasting abilities and damage.
But the thief herself is brash and impulsive; she attempts to pick locks on doors that are really just paintings of a door on a wall. And if the wizard is busy casting a spell, then the thief has no one to reign her in to tell her to stop attempting to steal maps from armor racks that look like stoic guards.
The analogy goes further. Because the wizard is old, he likes to conserve energy and even has mild sleep apnea. Or maybe he just likes to nap a lot. Either way, the wizard is not always awake. And when he is, he likes to do as little spellcasting as possible. The thief, however, because she's so young and full of vitality, is up and awake as long as you are playing the game. Choking in the clutch? Brain farts? Your wizard is either asleep and being a bit unresponsive or is being called into action when the thief had been trained by the wizard to handle the threat, and the thief had been casting that spell for the majority of the game.
Oh yeah, that's right. The wizard can teach the thief a couple of quick spells. But the thief doesn't have the large reserves of MP that the wizard has, so the thief can't cast huge spells. And if the thief does cast spell, it is a fraction of the strength that the wizard casts because of the thief's low INT.
Of course, your own personal thief has been active the entire time you've been reading this post. Your own thief already conjured up a narrative, a cast, costumes, and a setting for the symbolic thief and wizard in this post. That's what the thief -- System 1 -- does. Every day. With very little information it creates elaborate stories. What does your thief look like? Probably based on your standards of youth and beauty, with a little dash of mystery and guile. Maybe a dark-haired (elven) thief girl? That would be my guess anyway, but I'm not putting a lot of weight on it since I'm not a psychologist, I just play one on a blog. Your wizard was probably old and had a long white beard and a robe. Someone like Gandalf? Probably!
By the way, the thief? She isn't very good at differentiating between familiarity and veracity, yet she completely reigns over the unreliable feeling of certainty (so, for example, the thief would say that Christianity is familiar and confuse this feeling of familiarity with truth, especially without the wizard's input, and even more especially when the wizard is busy with another task or is out of MP). But that's why your wizard trust her; she's young and attractive.
Unfortunately, the wizard does everything that the thief asks him to do, especially attack positions that she doesn't like and defend positions that she does like. This applies to everyone. The wizard would not know who to cast a spell on without the thief's instruction or deference. When you read this sentence, it's the thief's responsibility to read the words. When you read 24 * 17 = ???, the thief reads that math problem and hands it over to the wizard.
Because of this, there's no such thing as a wholly rational human being with no emotion. Being emotionless would paralyze someone and they wouldn't be able to assign value to any task. I've read and listened to many conversion to Christianity (born again) stories. In these cases, the thief encounters and decides on the truth of Christianity before the wizard is even engaged. Or the wizard has been systematically drained of MP by the stresses of life and the thief is left to fend for herself. In either case, the wizard is only called into action to defend a position that the thief already decided on. I don't know anyone who became a Christian based on their thief's deference to the wizard before a conclusion was made about Christianity (or any religion, really).
Christianity is large and complicated; it is a final boss at the end of a dungeon. It would be unwise to use only the thief on a final boss, or only use the wizard after attempting to drain the majority of the final boss' HP with only the thief (here I would introduce a barbarian character as a compliment of the wizard: Intellect and reason. Also slow and subject to the same pluses and negatives as the wizard). That would be a horrible strategy in any RPG. The final boss would soundly pummel the thief and she would run out of HP and the game would be over very quickly.