There were different rules when humans were involved. (3.55)
For the dog, humans are the ones who make the rules. What aspects of the dog's life do these rules change? How is the dog's life different with humans from the way it was in the wild? And why does the dog end up preferring to be with humans rather than in the wild?
It was starting to seem to me that just when I had life all figured out it changed. (4.2)
Our main character is going to deal with this feeling for all his life. Er, lives, even. He never has it all figured out, at least not until the very end. But what are the odds that things might change for him even after the final page?
"There are no bad dogs, Bobby, just bad people. They need love."
"Sometimes they're broke inside, Senora. And nuthin' will help 'em." (4.18, 4.19)
By this logic, though, couldn't you say that there are no bad people, either? Do bad people just need love, too? Could you perhaps say the same thing about Todd, a human, later in the story? Maybe he is broken and nothing can help him. Neither our dog narrator nor any of the humans around Todd attempts to find out why he does what he does.
Of all the things I'd ever done, making Senora laugh seemed the most important. It was, I reflected, the only thing that gave my life any purpose. (4.81)
As the dog's idea of his purpose develops, this early conception seems quaint by comparison. It's even a little sad, since the dog sees no value in himself as he is; he only cares about making people happy. Does that core value ever change?
At once, everything was both strange and familiar. (5.1)
The reincarnation process is strange, although in a book narrated by a dog, we guess anything goes. The dog gets used to it pretty quickly, but he's also used to his own life being entirely out of his control.
My purpose, my whole life, had been to love him and be with him, to make him happy. I didn't want to cause him any unhappiness now—in that way, I decided it was probably better than he wasn't here to see this, thought I missed him so much at that moment the ache of it was so bad as the strange pains in my belly. (17.63)
Again, the dog puts the feelings of humans over his own feelings. He wants to die without Ethan seeing him, so as not to cause Ethan any stress, but he doesn't understand that Ethan might want to say goodbye. Also, is it possible that the dog is overestimating the amount of stress he might cause Ethan? Ethan may be upset, but the death of the dog isn't going to change his life that much.
That made me think of diving after the boy during rescue, the fading light as I dove deeper, the way the thick water pushed against my body, just like now. I could no longer feel the boy's hands touching me; I could just feel the water on all sides: warm and gentle and dark. (17.75)
These are Bailey's last thoughts before he dies. He doesn't know it yet, but he will be resurrected again, and these thoughts will become his new purpose—remember that he saves a kid from a storm drain at the end of his next life.
I understood, with a jolt, that I was a puppy again. No, that wasn't quite it. It was more that I was a puppy who suddenly remembered being me again. (18.2)
We get a few philosophical moments from our dog-arrator, usually right before dying or right after being reborn. Having that sort of experience tends to make someone—even an extra furry someone—a little introspective.
How could I, Bailey, be a girl dog? Except I wasn't Bailey. (18.8-18.9)
Bailey learns that nothing is impossible when he is reincarnated as a girl dog. Is there any real reason why he becomes a girl dog, or is what get here simply a bit of humor at his Bailey discovering that this time he's biologically different?
Dogs are not allowed to choose where they live; my fate would be decided by people. But I nonetheless felt torn inside, conflicted. (22.11)
As we showed in the first quote, rules are different when humans are involved. The dog doesn't think about things much when those "rules" make him feel needed. But when he doesn't feel needed, the dog is conflicted about his very existence. We can all relate.