"What is the primary purpose of Paul's writing of Ephesians?" "Which paragraph plays the most decisive role in identifying the primary purpose of writing Ephesians?" Motivated by complicated issues such as the difficulty of establishing a concrete historical setting, this thesis explores these two main questions from a linguistic-literary perspective. In addressing these questions, this thesis proposes a twofold argument: first, that Paul's primary objective in writing Ephesians is to encourage the Ephesian believers to build up the perfect body of Christ through the exercise of their Christ-given gifts until every believer attains Christ-like perfection; and second, that Ephesians 4:7-16 plays the most decisive role in identifying this primary purpose. An adapted version of J. P. Louw's colon analysis (a type of discourse analysis) is implemented for a formal (top-down/larger-scale) and systematic (cyclic) approach. Applying this approach, colon analysis facilitates the tracing of the author's flow of thought from proposition (colon) to proposition, and from paragraph to paragraph. This method investigates the structural division of Ephesians in order to answer the two main questions by first analyzing the entire discourse of Ephesians at a macro-level. Then it examines the internal structure of each paragraph at a micro-level before once again analyzing the whole of Ephesians in order to identify its primary purpose. To that end, various discourse markers (e.g., boundary markers, literary signaling devices, literary devices) are relied upon through the examination of literary features in Ephesians, which help to delimit each paragraph, identify the primary purpose, and determine the most plausible paragraph from which the primary purpose of the discourse is inferred. Since the value of colon analysis is derived from the analysis of the discourse at the macro level, close attention is given to the development of Paul's train of thought from paragraph to paragraph. This approach facilitates the discernment of prominent themes, illuminating the author's emphasis in a paragraph and how that emphasis relates to other paragraphs. Colon analysis also strikes a good balance between syntactical structure and semantic function of the Greek text while carefully examining the results acquired from both syntactical and semantic analysis. Therefore, this thesis concludes that Paul's primary intention of writing Ephesians is to inform the recipients of the ultimate purpose and goal of Christ's bestowal of at least one of the four (or five) gifts upon each believer: The body of Christ must be built (ultimate purpose) up to perfection (goal) by equipping God's holy people for ministry with those gifts until each of them (and the church as a whole) reaches perfection, i.e., the measure of Christ's fullness (goal). Consequently, this thesis contributes to the study of Ephesians by demonstrating how discourse analysis can help discern the author's chief intention, and how literary signaling devices and literary devices help unfold thematic and focal prominence, respectively. To the best of my knowledge, this is the first attempt to deduce (1) the author's principal purpose of writing the letter by means of (2) the pivotal paragraph for identifying that purpose in accordance with discourse analysis and discourse markers. Secondly, a top-down, cyclic approach to the text enriches the field of study by offering a thorough structure of Ephesians. Thirdly, because many New Testament scholars are unfamiliar with the practical use of discourse analysis in the interpretation of the NT, this thesis argues for its significance through its application in interpreting the text of Ephesians.