Some people describe morphology as the study of how words are built up; others describe it as the study of how words are broken down.

Some people describe morphology as the study of how words are built up; others describe it as the study of how words are broken down. What assumptions does each of these two descriptions make about how words are stored in our mental lexicons? Based on what you know so far, is one of these descriptions more or less accurate? Why do you think so?