Viewpoints on Selfishness

So, a couple of days ago, I read a book called "13 Gifts" by Wendy Mass. It's basically about a girl who moves to a different town, and learns a lot about herself, and the world around her. A lot happens in the book leading up to the morals of the story at the end, but there was one part I found particularly intriguing. Here it is:

I look down at my hands. "But you know I didn't do any of this for them. I did it all because you told me there was something I needed to know that I could only find out after putting on this play. I never stopped to think what anyone else needed, or wanted, at all. I can't take any of the credit."
She laughs. "Of course you can! Are you so self-centered that you think the universe cares what your motivations are? If a wealthy businessman donates ten million dollars to build a new hospital, would it matter if he only did it to get a building named after him? Not to the people inside it. If everyone waited to do something good until they had purely unselfish motivations, no good would ever get done in the world. The point is to do it anyway. To do it at all."

So, I started thinking about this, and I believe what was said here. I feel that there is always some sort of selfish motivation in everything, after all, we're only human. It might be an awful thing to think, but I feel like it's true. And there's nothing wrong with that, because we're human. Everything I do does indeed have a selfish motivation, and I'm not afraid to admit that. I'm not going to lie and say that I do everything out of the pure kindness of my heart, because I don't. And that's okay. I'm human.
Anyway, the day after I read that book, my English teacher was talking to our class, and completely contradicted everything this book just stated. Her words were something more like this:

"The whole idea of what I'm trying to teach you with this unit is to be a good person. Don't be selfish, do things because you know it's the right thing to do. For example, I know a lot of you have been asking me to sign your papers for NJHS. Well, who in here honestly wants to do NJHS for the good of it? To actually do your 15 service hours because it's the right thing to do? Instead of only wanting to be in NJHS so it'll look good on your applications and such? Maybe one or two of you, if any. The point is to do things out of the kindness of your heart, without any regards to yourself, or what you'll be benefiting from it."

So, I continued to think about it, and I still believed what I had read in the book. I asked my mom today what her opinion on the idea was, and she basically agreed with my English teacher, except she explained why:

"I completely disagree with the book. I refuse to believe that every single person on this Earth has only selfish motivations. You see stories all the time about people who do things just for the good of it. Who stay anonymous even when they do something that could change someone's life. There are people on this planet that are good enough to do everything out of the kindness of their heart. A lot of nice things could be done if everyone waited until they had purely unselfish motivations to do something. I refuse to agree with the book."

After that logic, I don't really know what to think. So, taking everything that has been said here, what are your opinions on this? If you'r reading this and you come up with an opinion, you don't have to post it as a comment or anything. Just think about it. Figure out your idea of goodness. Is everyone on Earth really selfish like that? Or is it the other way around? Just think about it. And if I've provoked you enough, write about it. I hope I inspired something.