From The Life of the Cosmos by Lee Smolin.
No wonder physics is so hard to learn. As it is usually taught to students, Newton’s physics does not make complete sense, for they are almost never told the whole story. Position, velocity, and acceleration are usually introduced as if they have simple and obvious meanings, but the do not. Even more difficult are the concepts of force and mass; the definitions given of them in textbooks are almost always circular. The students are seldom told that if they are puzzled it may be for good reason, or that the things that confuse them have been debated for centuries. Some figure it out for themselves. Many go away with an unjustified sense that they cannot learn science.