What is the function of Yi Gua?

Change is the only way to change your mind. The so-called change refers to the change of an event. If a hexagram does not change, there will be no change. Naturally, if you only look at the hexagrams, you can't see the change, which can also show that the measured things have not changed. However, everything is changing, how can it never change? So, this is just a reference. Generally speaking, we should not be too extreme, and we should understand it flexibly in order to make good use of hexagrams.