ABSTRACT
One of the hard problems in the study of human cognition is how it should be modeled. While it is taken for granted that models are necessary in the study of cognition, just as in every other field of science, there are two issues of the model problem that need to be addressed. One concerns what should be modeled; this is the issue of the substance of modeling. The other concerns how the models should be expressed, i.e. the language of modeling, or the technical issue. This article only discusses the former.
