Yin and Yang - The opposites in balance
Yin and yang represent all opposite things and the way they need to be in balance in order to exist. This opposite aspects representation and their theory are extremely important for feng shui. Actually, you can say that feng shui is based on them and all feng shui notions and tools follow this concept.
According to yin and yang theory, there is a permanent tendency to balance between opposite forces. Right and wrong, winter and summer, they always contain some of its opposite and are always interacting. According to this, there is nothing completely good or completely bad, and there is nothing permanent. All opposite aspects are always going through a cycle and looking for balance between each other.
These opposite forces are co-dependant and can not exist without the other. The concept of right couldn't exist without the concept of wrong and they depend on each other for their existence. Therefore, each force is always present within its opposite and lives through it. This is what the feng shui notion of balance is based on; everything is always tending to balance. Any distribution of elements must tend to balance in order to be healthy.
Yin symbolizes the passive, cold, even, moon, water, death, winter, female and night. Yang symbolizes yin opposites such as active, hot, odd, sun, fire, life, summer, male and day. Each one of these aspects exist since its opposite exists and they both depend on each other to continue their existence. According to this, one opposite is born and grows from the other, and as one grows and the other tends to loose power, this last one starts tending to look for gaining predominance back again. This is a constant process which makes natural elements be in constant look for balance through the existence of each other.
There is always some yin within yang and there is always some yang
within ying. Yin and yang theory is based on the most basic nature laws,
which show yin and yang in everything which surrounds us. Feng shui
is based on this yin and yang natural constant search for equilibrium,
and intends to balance the natural elements in spaces and environments
which were created by human beings without taking those laws into account.