抄録
In this study, qualitative analyses on opinion essays written by highly advanced students were undertaken from a perspective of the effectiveness of "concession" for strengthening the validity of one's opinion. From the analyses, the following three pairs of effective "concession" and ineffective "concession" were identified: 1) logical and natural "concession" and abrupt "concession"; 2) "concession" with a valid counterargument and "concession" without it; 3) concise "concession" and too long "concession."
