Traditional Chinese medicine analyzes pathological factors on the basis of clinical manifestation of symptoms and signs. These disease-causing factors can be triggered by external influences such as variation of weather, irregular food intake, stress, lack of physical activity, and traumatic injuries. Internal (or emotional) factors can also cause disease. There are seven main emotions: joy or excitement, anger, sadness, worry, grief, fear and fright. Therefore, no two illnesses are ever the same because each person's internal and external influences interacting together create a disorder specific to that individual. This is a very different view from the practice of Western medicine. In most cases, Western medicine treats the body, mind, and external factors separately and does not necessarily view them as interdependent parts. For example, an Ophthalmologist treats only an eye problem. A Chinese doctor will look at an eye problem and ask "how is your liver?"