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A man is comprised of three parts, a mind, a body, and a soul, each of which are reliant upon the other and all of which can be understood via the Machine Gods science and faith.
We know a mans body is weak if deprived of food, sleep, rest, but even the fittest natural body pales to those augmented and provided the best environment to train it. Enhanced genetic sinews, Catalepsean/Cybernetic sleep replacers, artificial food dispensers, plus rigorous physical endurance training. Genetics can result in a far stronger breed of body such as Ogryns or Astartes.
The same is proven true of the mind. Through education and determination a man becomes smart. But even normal human limits can be exceeded through science. Cybernetic augmentation, brain tissue enhancements, hypnomat and information uploads. These are the things that separates the smartest man from the smartest techpriest.
Even the soul. Courage and bravery are a combination of hormones as adrenaline and cortisol, cultural upbringing and history, and the genetic neurological makeup of his mind that predisposes one to fight or flight, bravery or cravenry. As we have seen from Skitarii and Astartes, these too can be augmented, with either cybernetic fear suppressants or genetic ones as the Astartes who "know no fear". As the mind can be educated, the soul can be taught via faith, rites and the religion of the machine cult.
Talos is a Techpriest. He is at once genetor of the body, neurologist of the mind, and psychologist and preacher to the soul. I'm sure he could come up with many ways to boost the chances of Princep aspirant survival from both science and faith.
Perhaps he could offer the Princeps families to make their aspirants a little bit like psudo-acillians, so their bodies are less likely to reject the implants and minds enhanced and educated by knowledge and faith with direct insight to the nature of machine spirits by Talos to give them the best chance to not be overcome by the machine spirit. It would give them more material to work with higher chances of survival.
We are the only Primarch to truly become one with a Titan's machine spirit and speak to it. Something not even Perturabo, Ferrus or Vulkan did! Imagine what knowledge or improvements to the training program Talos could impart as perhaps the greatest Princeps the universe has ever seen. I mean, unless the Emperor ever wanted to drive a Titan for fun in the Dark Age.