2. THE DEBATEThe idea of ​​including L1 in the language teaching system has been debated in recent years. Strong anti-L1s suggest a total ban on L1 in classrooms, while many others see L1 as a tool to improve students' LT learning. This section will highlight the pros and cons of using the L1 in the classroom, along with further evidence to support the benefits that the mother tongue brings to the language learning and teaching process.2.1 ARGUMENTS AGAINST USING THE L1 IN CLASSROOM In the twentieth century, avoidance of the use of L1 in the classroom dominated teachers' minds; it has also been implemented in many language teaching policies and guidelines (Cook, 2001). Thornbury (2010) listed a number of arguments against the use of L1 in L2 classrooms, mainly because translating the L2 into another language will have negative effects on the students' learning process. He emphasized that the use of L1 will lead students to have a cognitive dependence on their native language to the detriment of developing independence in TL learning. Although the two linguistic systems are not equivalent in many respects, students can be aware of the concept of equivalence of the two languages ​​if the translation serves to convey meaning. Some argue that using translation to convey the meaning of the LT is more efficient and easier to remember. However, Thornbury (2010) sees the opposite. He stated that the simple and direct way of translating will make L2 knowledge less memorable as the process lacks mental effort to process meanings. Many researchers such as Krashen (1985), Harmer (2007) and Turnbull (2001) point out that in most EFL (English as a foreign language), the teacher's knowledge of English... half of the paper... L1 for instructions and assessments to avoid confusion. On the other hand, teachers prefer to use L1 for a more effective approach to teaching grammar and checking students' understanding. Macaro (1997) commented that teachers often lack enthusiasm in using the target language for grammatical explanations. Many students have difficulty learning grammar, especially those whose L1 system is completely different from the LT. The L1 can be more efficient, particularly when a teacher wants to discuss the learning contract with students, or tries to explore the needs of his or her students, especially those at the lower level (Harmer, 2007). Evidence provided by Harmer (2007) also indicates that the classroom environment can be improved through the use of L1 to establish a positive social relationship with students, which ultimately leads to a more effective teaching process..