Theme, as a point of departure plays a crucial role not merely in the organization of the academic messages but also in the functions of the clause, such as the notions of authorial voice and critical thinking. Halliday (2004) defined theme as an element that serves as the point of departure, identified by its position in the clause. This means the use of the main idea and/or author in the subject position stem of any clause is very important in presenting the elements of critical thinking and self-voice. This raises an important question of how postgraduate students as academic writers deal with the function of Marked and Unmarked themes as a point of departure in demonstrating a critical argument. This study, therefore, attempts to see how the functions of the Marked and Unmarked themes in demonstrating a critical argument are tackled by the academic assignment writers. Applying Halliday's (2004) model of thematic organization, this paper investigated a corpus of four academic assignments from four Masters Students (two Iraqi non-native and two Australian native writers of English). The results showed that Australians were more visible in displaying the elements of critical thinking and self-voice as a dual competence for their writing, while these elements was invisible in the Iraqi writers as they gave their loyalty to their textbooks and course materials. This findings will provide not only Iraqi postgraduate students with a better understanding of problems in order to help them improve their authorial voice and critical thinking in demonstrating a critical argument, but will also for Iraqi EFL instructors at the Iraqi universities on what exactly needs to be made explicit within the framing and language of the academic assignments.
Theme, Iraqi Non-Native Writers of English, Australian Native Writers of English, Marked Theme, Unmarked Theme, Critical Thinking and Self-Voice.