Should Contain Education should have a pragmatic purpose.
Education ought to be about building learners' abilities to do useful things.
What is important to learn is whatever helps learners do things that they want to do or that they can be induced to want to do. Therefore, if we want to detail the knowledge students need to have, we should first detail the things students should know how to do. Then we can determine what knowledge will be useful in each case. Depending on an individual's situation and goals, there are many things that might be worth learning. In order to give a very detailed prescription for what knowledge a student should acquire, we must take into account that not every child will need or want to do the same things.