What are the merits and demerits of the grammar-translation method of language learning?

The grammar-translation method of learning a foreign language almost exclusively excludes oral production and strictly emphasizes written work in translation based on learned prescriptive grammar of both the target and native languages. In the grammar-translation method, the student masters the native language grammar as well as the target language grammar and correctly translates passages of one language to the other; this requires application of both grammars in order to attain the correct translation.

Based on an article by Nancy Thuleen of the University of Wisconsin-Madison, the merits of this method of language teaching and study are that (1) dead languages can be studied and preserved; (2) the grammar of the target language is mastered; (3) translation skills are mastered; (4) it facilitates the learning of students who having learning styles leaning toward left-brained originated comfort with rules and structure and who respond well to correction between right and wrong answers.

Some of the demerits of the grammar-translation method, again according to Thuleen, are that (1) teaching is not done in the target language, so social contextual exposure is essentially eliminated; (2) oral practice is almost entirely excluded, which is a great drawback because students' original sentences are not produced despite language being primarily oral; (3) mastery of the target is judged purely on translations, which, if done well, are the sole indicators that the language is known well; (5) it is a learning process in which error correction is necessary to advancement, putting the student in a defensive learning position, which may impede some student's learning of the target language.