"Normal science" is not the whole picture.
Kuhn's book is centered around this argument, that without putting normal science in its proper context, and understanding its uses and limits, we will misunderstand the nature of scientific inquiry. Basically, science is rooted in skepticism, for Kuhn, because scientists are tasked with understanding the scientific past (receiving a "received" tradition), but then they should hold those views in perfect tension, because science is dynamic. The only thing we can know for sure is that on almost everything, we've been wrong in the past, so there is no doubt that we probably misunderstand some things.
Paradigm shift is like political shift.
Much of this book treats this idea directly: that the best analogy to understand the way scientific progress really looks on a technical level is to understand it in terms of political revolution. By understanding the communal nature of science, it basically proves itself that it is political, because the community is a community of real humans who understand science through whatever paradigms they use to understand the world. And, since Kuhn believes that each new scientific discovery comes with an implied world view change, it's no wonder why scientific revolutions have to play themselves out—world view changing is serious business.
We must continually seek to understand truth.
When we say that a fact is "true" scientifically, what does that mean, as opposed to truth in other settings? Kuhn answers that we can never believe that our current explanations are necessarily correct, which means that he is invoking the subjectivity of our experience of nature and reality. Therefore, he says we should hold our believes in tension with the full weight of our scientific imagination, because even when the tests are trustworthy, we are trying to understand a universe that confounds our imagination often. We take it as truth that the sun is the center of the solar system (to use one of his early examples). But, before that, we took it as truth that the earth was the center of the universe. What changed is that our view of truth evolved alongside science, and Kuhn says that's exactly the point of science done correctly.
