The fact that Pi grew up in a zoo is very beneficial to what happens to him. With the freedom aspect, the whole concept of a zoo is the opposite of freedom-restriction. Watching captivity and restriction in action makes freedom easier to understand. When you know the reaction of restriction, and what it does to something, you understand better what it means to be free and the difference freedom and restriction. And even us as humans are animals, and are so similar in so many ways to the creatures that live in captivity. This makes it easier for us to understand them. Because the more someone knows the less scared we are to learn more. So the more Pi knew about these animals and what captivity did to their heads, the more he knew how to deal with being in the same situation. So knowing the feeling of being free, taught him how to deal with being captive.
I think that the fact that Pi is exposed to so many ways of life in the zoo, through each kind of animal, he grew to realize that he should have a way of life. He also realized that everyone was different. So why should he just choose one way of life to follow? Why not explore many ways of life, and create one of his own? I think he realized that even if someone is captive physically, they can still shape how they react, live and think. So he thought that even though he isn’t captive physically, why be captive mentally? Then when he finds himself physically captive, he knows how to protect himself from becoming mentally captive, and chooses to not allow his mind to be seized by really pondering what he has learned throughout his life in the zoo and religious studies.