If pissing yourself was just a perception (and in this context it is strongly implied that it is the perception of the one who is doing the pissing) then it would hold that others nearby would not have this same perception. In common practice, though, when I piss myself I perceive that I have done this (cold, wet feeling in my pants,
smell of urine, etc) BUT: others also perceive it (as evidenced by the calls of: "Hey, mate, did you just piss yourself?").
Furthermore, only people within the range of sight and smell (and possibly hearing) are able to perceive my pissing myself. This would infer that there is a direct correlation between the physical reality
of my having pissed myself, and other people perceiving that I had. Since I, myself, have perceived my own social error, AND those in close enough proximity also perceive it, but people maybe a mile away cannot perceive it (unless they have a telescope, or some sort of X-ray vision - or one of those portable long-range smelling devices that fit into your pocket unnoticed) it leads me to believe that the 'index offence' was part of a physical reality - and not just a subjective perception. I realise this is nothing more than inductive reasoning, and does not confer absolute proof, but I believe it represents a strong argument.