There is a certain amount of awkward incompatibility between the linguist's use of underlying syntactic structures and his assertions that such structures have psychological validity, particularly in the light of some recent psychological research. Nevertheless, the linguist's use of deep structures can be justified if we will re-state our goals and claim to describe langue rather than competence.
"Non-Psychological Deep Structures?,"
Colorado Research in Linguistics: Vol. 6.
Available at: https://scholar.colorado.edu/cril/vol6/iss1/3