@article {IOPORT.05059458, author = {Carter, Nathan C.}, title = {Reflexive intermediate propositional logics.}, year = {2006}, journal = {Notre Dame Journal of Formal Logic}, volume = {47}, number = {1}, issn = {0029-4527}, pages = {39-62}, publisher = {University of Notre Dame, Notre Dame, IN; Duke University Press, Durham, NC}, doi = {10.1305/ndjfl/1143468310}, abstract = {The author modifies the formulation and proof of a theorem due to {\it D. C. McCarty} [Notre Dame J. Formal Logic 43, 243--248 (2002; Zbl 1050.03041)] to get the following statement: Let $T$ be a second-order theory based on a superintuitionistic logic. If $T$ proves the completeness theorem (consistency implies existence of a model) for some superintuitionistic propositional logic, then $T$ proves every instance of $\neg\varphi\vee\neg\neg\varphi$. The proof uses very few properties of $T$ except comprehension. Defining $A= \{p\mid\neg\varphi\}\cup \{\neg p\mid\neg\neg\varphi\}$ and $B= A\cup\{p\vee\neg p\}$, $B$ is consistent since both $\{p\}$ and $\{\neg p\}$ are. By completeness, there is a model $M\models B$, hence $M\models p\vee\neg p$, so $\neg\varphi\vee\neg\neg\varphi$.}, reviewer = {G. E. Mints (Stanford)}, identifier = {05059458}, }