This paper explores the principles of Taegeukgi and considers that the philosophical spirit of Taegeukgi has achieved the core of Korean thought and living culture from ancient times to today, and argues that it still has a valid meaning in the future. First of all, Yijing thought which the Taegeukgi contains, is not an exclusive property of a particular country or nation, but a universal philosophy of Northeast Asia. The owner's qualifications are not based on origin, but on the narrative that has been embodied in life and history. The complementary thinking of yin and yang, love of life, resistance to anti-life violence, and humanitarianism are consistent from Dangun mythology, to Choe Chi-won's Pungnyudo, Neo-Confucianism, Donghak's "people are the heaven.", and Jumgyerk. The representative symbol is the Taegeukgi. Koreans have lived their lives by deeply internalizing the idea of Taegeukgi. Today, when people around the world recognize the symbol of Korea as the Taegeuk mark, the representative of the Taegeukgi ideology is definitely Korea. Korean society, which has miraculously achieved material prosperity despite the colonial invasion, the Korean War, and the crisis of the IMF, is about to achieve a second miracle in terms of mental culture. As the core of Korea's long-standing history, the Yingyang thinking of the Taegeukgi is an excellent framework to explain Korea's potential for overcoming many crises. It contains humanistic values that must be recalled in seeking a K-philosophy that can spread beyond Korean society to universal values of mankind.