On reading this
"How can I know that another person is truly in pain?
In Stanley Cavell's memorable restatement of the problem let's imagine that I am a dentist drilling a patient's tooth and the patient suddenly screams out as a response to what seems like the pain caused by my clumsy drilling. And yet, in response to my embarrassed show of remorse, the patient says 'No, it didn't hurt, I was simply calling my hamsters'.
Now how can I know that the other person is being sincere, short of his hamsters scuttling obediantly (sic) into my dental surgery?
The point is that ultimately I cannot. I can never know whether another person is in pain or simply calling his hamsters.*"
I stopped and thought "This is a torturer's defence":
Prosecuting Counsel -"Did you realise you were causing pain
when you applied the drill to his teeth?"
Torturer - "No. I thought he was calling his hamsters".
This may be a defence based on a strict epistemological interpretation of "know" but a more pragmatic approach is called for based on empathy ("if this was happening to me I would be in pain") and a sense of human decency, if we are not to justify some evil acts.
*[Critchley, Simon. The Ethics of Deconstruction - Derrida and Levinas.
2nd ed. Edinburgh: Edinburgh UP, 1999. 285.]