Here before you is a person in pain. Do you deduce that they are in pain by some form of induction from their behaviour? — Banno

Context matters. If I suspect this person is trying to get money from me for drugs, that will influence my interpretation. If the person turns toward me and I see his arm is dangling by a tendon, I'll change my mind.

Or do you see that they are in pain? — Banno

Look at the bolded part. It's a proposition. The eyeball does not see. The mind does.

Is their pain expressed, or is it shown? — Banno

What's the difference between expressing emotion and showing emotion?

Odd thing is that one sees the pain in an actor, then becomes convinced that it is an act. It's not the other way around.

Do you look at the jerking, back arching, teeth gritting, and press out that they are in pain?

Or is it right there to be seen in front of you?