According to classic Chinese cosmology, which has its foundation in the "I Ching", the above evolvement explains the creation, growth, extinction and change inherent in the natural world. The "I Ching", or "Book of Changes", is a source for later Chinese thought and culture, and dates anywhere from 3000 to 1200 BC. Much of the philosophical thought and many elements of culture diffused from China to other parts of Asia and influenced ideas about the dual nature of the world.

Ancient artists utilised the characteristics of Um-Yang theory in developing techniques and principles. Seen in this way, Um refers to soft, elastic, close and circular nature while Yang refers to a strong, stiff, angular, distant and straight nature. These two forces steadily interact in laws of contradicting yet complementary opposites, and their continual resolution is called "dialectic development". For example, in Ho Sin Sul we apply a circular defensive motion against a linear offensive attack. This is a classic case of the complementary interaction of opposites. Done properly, the Ho Sin Sul movement can be executed smoothly and effectively to counter the brute force of the attack using the Um-Yang principle of the interaction of soft against hard
The deeper studies into the Um-Yang theory led to the realisation of "Ki" which is known as the principle source of human power. This power exists in everyone and is nourished through proper breathing, among other things. Again the Um-Yang principle of opposites making a hole is emphasized in the breathing in and exhaling out of oxygen. Practicing good breathing habits allows the Tang Soo Do student to enhance and manipulate Ki power to achieve a healthy balance with the universe. Therefore, learning Tang Soo Do is not the simple achievement of techniques, but it is the learning of a way to discover the link of the external universe to the personal inner universe of the body.

The graphical symbol of Um-Yang is a circle with an inverted figure "S" in the middle. The "S" represents the principle of dynamic movement constantly ascending and descending. The dark side represents Um and the light side, Yang. Each side has one eye which is a seed of Um in Yang and vice versa. Each side, therefore is an integral part of the other and assures their complementary interaction

The resulting elements of the interactions, the creation of Um-Yang, are manifested as bar groups of solid lines (Yang) and broken lines (Um). Ancient wisdom and divination (which is the art or practice of trying to tell the future or the unknown by occult means), was employed to develop this alignment and the division of the bars. The solid and broken lines are most often expressed in combinations of three and are called trigrams. There are two popular sets of trigrams. One is comprised of sixty four bars with six line symbols called hexagrams and the other is compressed of eight groups of three lines. These symbols are call the Pal Kae trigrams.

Tang Soo Do strives truely to understand and appreciate nature, and apply, in a practical manner, the laws of nature. Central to this fundamental concept of the art of Tang Soo Do is the Um-Yang theory which is based on a world of opposite, yet complementary and harmonious parts. This idea is not so far removed from the computerised world in which we live today. In Fact, the basic operaiton of a computer are based on the sue of binary digits, 1's and 0's, to communicate with the electronic brain. Binary in this case means a whole composed of two. The Um-Yang theory, though similar, goes beyond the mere operation of a computer because it considers that the entire universe, and everything in it , can be described and understood in terms of the simple ebb and flow of polar or binary opposites.

From the early days of Oriental cosmology there have been many efforts to understand and explain the creation, evolution, and structure of the universe. From these efforts there emerged a theory of natural dualism called the Um-Yang. The theory was founded through the efforts of Chu Yeon in approximately 300 BC. Classical oriental cosmology argues that Um-Yang are the two very basic properties of the universe and that these two extreme forces make creation, growth, extinction, and change in the natural world.
Yang is characterised by male, light, heat, and positive, Um stands for female, dark, cold, and negative.
When these two forces interact, by meeting and parting, they evolve into the five elements of nature: wood, fire, water, metal, and earth. Although today we recognise more that 100 known chemical elements, the early oriental cosmographer, or scientists, recognised only these five, and together, they made up "Nature". It is quite interesting to learn that other ancient civilizations developed a philosophy of the elemental world much like the Orientals. For example, in ancient Greece, there was a similar theory of elementary composition stating that the universe was composed of four elements; earth, fire, air, and water. Whether in the East or West, it was assumed that the balanced of these elements kept the world in a "natural" equilibrium.

In Oriental cosmology, the world was symbolised as a circle consisting of the five elements which are in constant interaction with each other in a circular fashion. The following diagram shows each circular direction and the interaction of the elements with each other.