Like the narrator of Robert Frost's poem "Mending Wall," instructors need to ask what is being walled in and walled out of their composition programs when categories such as process vs. product, expressive, epistemic, current traditionalism, and social constructionism are constructed. When divisive categories prevent theorists from receiving worthy consideration, then descriptive fences have become exclusionary, prescriptive barriers. As the dialectical philosopher John Dewey warned, humanity "likes to think in terms of extreme opposites. It is given to formulating beliefs in terms of Either-Ors, between which it recognizes no intermediate possibilities." For instance, when Ken Macrorie and Donald Murray and their writing-process colleagues wanted to advocate their new rhetoric, they engaged in divisive thinking with their process "versus" product approach. A Deweyian reconsideration of Don Murray leads to criticism of the "expressivist" label applied to him by Lester Faigley, James Berlin, and others. Rather than engage in divisive and reductive "Either/Or" thinking, it is necessary to preserve the valuable contributions of inevitable incomplete writing theories like that of Don Murray. By avoiding dangerous dichotomies based on thinking in extreme opposites, writing instructors fulfill Dewey's belief that socially constructed knowledge exists both through its transmission between individuals and its constant reconstruction by individuals. (Contains 27 references.) (SAM)