The idea of "the power of one" is a recurring theme in the novel, and Peekay brings it up several times as he grows up. The first time he comes across it is when he has to go back to boarding school and the bullies after holidays at the farm:
Ahead of me lay the dreaded Mevrou, the Judge and the jury, and the beginning of the power of one—how I learned that in each of us there burns a flame of independence that must never be allowed to go out. That as long as it exists within us we cannot be destroyed. (2.8)
This idea will continue to develop throughout the novel as Peekay grows up and is influenced by the various characters that he runs into:
[Hoppie] had given me the power of one—one idea, one heart, one mind, one plan, one determination. (7.4)
Doc will also give Peekay some superpowers:
Doc had taught me the value of being the odd man out [...]. The power of one was based on the courage to remain separate, to think through to the truth, and not to be beguiled by convention or the plausible arguments of those who expect to maintain power. (17.71)
It's interesting that Peekay learns the power of one only through his relationships with other people. It's like you need more than one to have the power of one. So does this mean that Peekay's philosophy is just a bunch of hogwash? No! It might be a little ironic, but it was still very important for him to learn to be independent and fight for himself because, as we know, he loses friends right and left.
As he gets older, Peekay is able to articulate what exactly he means by "the power of one." It's not just a feeling anymore, but a philosophy that he can define:
The power of one is above all things the power to believe in yourself, often well beyond any latent ability you may have previously demonstrated. (21.121)
This means that people who should have no hope of winning (like a dinky kid against a giant gorilla in a boxing ring) can find some sort of crazy belief in themselves that helps them do the impossible, just like Peekay. Better start looking for your inner mystic waterfalls, Shmoopers—who knows what kind of strength you might find.