The purpose of this thesis is to convey and to support my belief that learners' affective domain, which consist of their personalities, attitudes, and motivation are responsible for causing the variation in the levels of second language proficiency of second language learners. My concern is to point out or support others who believe that second language learners are not machines that are able and willing to be programmed; they have feelings and attitudes which in turn govern their personalities and motivation. I also believe that the main focus of second language teaching should be on the "persons" learning the language, instead of merely on the forms, rules, and structures of the second language itself. I hope that this study will provide insights to all second language teachers.