The Indian poet Rabindranath Tagore compares the function of evil to the banks of a river.

Buddhism Day by Day

Wisdom for Modern Life by Daisaku Ikeda
Sunday, May 25, 2014:

 

The Indian poet Rabindranath Tagore compares the function of evil to the banks of a river. The riverbanks are obstructions, but they are necessary for keeping the river on track and flowing steadily forward. Without banks, the river would overflow, causing destruction instead of creating value.