ERRORS (NOT MISTAKES) MADE IN BOTH SECOND LANGUAGE LEARNING AND CHILD LANGUAGE ACQUISITION PROVIDE EVIDENCE THAT A LEARNER USES A DEFINITE SYSTEM OF LANGUAGE AT EVERY POINT IN HIS DEVELOPMENT. THIS SYSTEM, OR "BUILT-IN SYLLABUS," MAY YIELD A MORE EFFICIENT SEQUENCE THAN THE INSTRUCTOR-GENERATED SEQUENCE BECAUSE IT IS MORE MEANINGFUL TO THE LEARNER. BY ALLOWING THE LEARNER'S INNATE STRATEGIES TO DICTATE THE LANGUAGE SYLLABUS, RATHER THAN IMPOSING UPON HIM PRECONCEIVED NOTIONS OF WHAT HE OUGHT TO LEARN, A MORE EFFECTIVE MEANS OF LANGUAGE INSTRUCTION MAY BE ACHIEVED. THIS ARTICLE APPEARED IN THE "INTERNATIONAL REVIEW OF APPLIED LINGUISTICS IN LANGUAGE TEACHING," VOLUME 5, NUMBER 4, NOVEMBER 1967, PAGES 161-170. (AF)