#A central change of model, metaphor, or analogy-a change in one's sense of what is '''similar''' to what, and of what is '''different''' (分类的变化), is very important.
#The language of twentieth-century chemistry can be used to identify referents of the terms and expressions of eighteenth-century chemistry, at least to the extent that those terms and expressions actually refer.
#In learning Newtonianmechanics, the terms 'mass' and 'force' must be acquired together, and Newton's second law must play a role in their acquisition. One cannot, that is, learn 'mass' and 'force' independently and then empirically discover that force equals mass times acceleration.
#Interpretation is the process by which the use of those terms is discovered, and it has been much discussed recently under the rubric hermeneutics.
#Such texts (intended to teach them the language in which such texts are written and the way they are to be read) are also encountered by people who have already learned to read them, people for whom they are simply one more example of an already familiar type. These are the people to whom such texts will seem merely translations, or perhaps merely texts, for they have forgotten that they had to learn a special language before they could read them.