The Lizard on the Wall

Today, whilst sitting on the verandha with my father eating lunch, he started and said to me: "Look at that little lizard over there on the wall!".
I looked over my shoulder and indeed there was a small skink laying in the sun on the vertical face of a limestone step. I replied: "Oh yeah, I've seen him about three days in a row now",
to which my father nodded indifferently and went back to his slow-cooked free-range pork chop. After this transaction I wondered whether it had in fact been the same lizard, or was it just another one?
A few seconds later my father again started, and said: "Look, there's another one, there're heaps of them, no wonder you thought you'd seen the same one". Again I looked over my shoulder and there indeed was another skink, although notably larger than the other. I said to my father around a mouthfull of buckwheat and pumpkin stew: "Possibly, but I'm certain it was that same smaller one".
Again I wondered about the fact of it being the same lizard as I believe, or a different lizard as my father seemed to believe. It then occured to me, and as there was no way of testing or using 'hard' fact (as people, rather illogically, seem obsessed with these days) to determine whether it was or was not the same lizard, it became apparent, indeed become a 'fact', that it must have been the same lizard, as well as being a different lizard.
The observer will always have an effect on the observed.