This study is to constitute a framework for understanding aesthetic sensibility by introducing a mental model called the content space which is defined as a set of all possible contents of consciousness. An aesthetic sensation is a conscious process, thus it belongs to the content space. On the other hand, all mental process must be realized by neural activities which were initially evolved in human ancestors. Because aesthetic sensation is a content of consciousness appeared only in human, it is highly probable that its origin can be explained by a correlating process of biological evolution and cultural development. As the bridge between mental and physiological processes, the emotion and mood relating aesthetic sensation are also considered in the proposed model.