The basic distinction in Advaita Vedanta–namely, that the Seer is different from the seen–can be restated thus: the Witness is different from all objective experiences. 

Now, if the Witness is different from all objective experiences (namely, thinking, feeling, perceiving, and sensing), then It can’t be affected by the content of any objective experience?

To explore this, you can ask:

• Does this experience–e.g., seeing, touching, desiring, feeling, thinking, etc.–in any way change Me, the Witness?

You might wish to look closely at these cases:

• I am in pain.
• I am experiencing intense emotions.
• I am experiencing intrusive, compulsive thoughts.

Does pain impact–change, alter, modify, indeed hurt–Me, the Witness? Does anger? Do vengeful thoughts?

No, but the invitation is to see this for Yourself.