Why did the writer use "another subject altogether"? When I was a young girl, my room was always a mess. My mother was always trying to get me to straighten it up, telling me, “Go clean your room!” I resisted her at every opportunity. I hated to be told what to do. I was determined to have my room the way I wanted it. Whether I actually liked living in a messy room or not was another subject altogether. I never stopped to think about the benefits of having a clean room. To me, it was more important to get my own way. And my mother, like most other parents, did not get me to realize the benefits for myself. Instead, she decided on lecturing. Whether I actually liked living in a messy room or not was another subject altogether. Why did the writer use "another subject altogether"? Of course, I understand this sentence but I don't know why another subject appears.