Purity of mind requires the destroying of all bad impressions collected there or received at present. One can destroy these impressions by five methods, and the method is chosen according to the impression one has to destroy.

1. Some impressions need to be washed off from the mind;
2. some require to be erased from the surface of the mind;
3. some have to be shaken off like dust from the clothes;
4. some need to be burnt like the wood in the fire, which after its test by fire turns into ashes;
5. and some impressions must be drowned, so that they will never come up again.