This is a good question. I think there are several ways to answer this question. First, you can say that the chorus has helped Antigone come to her conclusions and convictions. In this sense, the chorus was essential. However, you can also say that the chorus was unsuccessful in two ways.
First, Antigone would probably have buried her brother no matter what. She is a woman of conviction. There is a strong moral fiber to Antigone, which her sister lacked.
Second, it can be argued that the chorus actually failed in the end, because Antigone commits suicide. The chorus was not able to prevent this or prevent Creon from his course of action. In the end, I would argue that the chorus was not essential to Antigone's actions.
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