Chinese Medicine
In Chinese medicine, we actually regard the world like physicists do: everything is energy. Depending on the energy quality, something is solid, liquid, or gaseous, moves at different speeds, and is changeable. Energy flows inside people as well. If it flows correctly, we are healthy. If not, it can cause disorders that we call malaise or illness.
In Chinese medicine, we call this power Qi and it moves and changes throughout our lives. In the condensed state, it forms our body and corresponds to Yin. If the Qi is moving, it's Yang. Yin and Yang are constantly changing and thus allow birth, growth, reproduction, movement, and development.
Actually, Chinese medicine serves as a preventative measure. Similar to how you change the oil of your car every 10,000 km or have it inspected, it is also important to regularly check your wellbeing. The Chinese say that nature (and its energy) fluctuates with the change of seasons. Likewise, the energy in humans changes too. Traditionally, the Chinese then go to the doctor to make sure that the Qi are in harmony with nature and to correct any imbalances. If the person gets sick anyway, the doctor is fired.