Nagel used the term subjective character to describe one of property of our consciousness. In his paper, the definition is hard to understand directly. However, by his definition we can know that for an organism to have consciousness is for itself to feel like to be itself, which means such consciousness is only working for that organism and associated with that organism is a basically property. This term is saying that our consciousness is a subjective experience of our self only. For example, feeling happy is a mental activities and it is subjective. Everyone may express themselves by saying or showing that they are happy but the exactly feeling for a person will never be experienced by anyone else. Such a feeling is working on you and “happy” itself is a part of consciousness which is saying that if you want feel all the same that someone else feels, then you must have all your consciousness the same as that person.
In order to make this term clearer Nagel introduced the example of what is like to be a bat. He argues that we cannot know what a bat experiences for some reasons. First, he