Two opposite energies
Two opposing energies together create a problem and this is a fact in everything we come across. Like day and night, fire and water, winter and summer, man and woman, etc. So if we can balance them then we can have a perfect world. Everything in the universe, we know has two opposite energies which try and oppose each other, but at the same time they need each other. Nothing can exist or last long without the opposite energy. In this way two opposite energies together forms one thing. Think of yourself, you are flesh and bone or mind and body, and these things must be together.
Taiji is two opposite energies together and is one thing – one unit, like man, like a table, a house, one country, one universe. There are always two opposite energies together and we just need to make them balance. Therefore we see the Taiji symbol is half black and half white. The black means night time and the white means day time. This is how the ancient Chinese discovered these two opposite energies together and how they make nature work and continue. This is the true meaning of Taiji.