Not one existing and one perceived

We begin with an example. While walking, I see a stone by the road and kick it. (...) Years after the event, I remember the scene of my kicking the stone. 

Two features of this example are relevant. In the first place, there is the fact that I kick, imagine, see the same stone. In the second place, when I remember the stone I kicked, my evidence for remembering the same stone is beyond question. (...) I may recall at will the event of my kicking the stone, and the stone remains the same every time I recall it. (...) Anything I see, anything I think, anything I deal with carries the possibility of being seen, thought or dealt with again. (...) With each and every act of seeing I presentify an item. In every presentification, the item maintains its identity. The stone I remember is the same stone I kicked. (...) It is a mistake to believe that what I kick is a material stone. If the stone were a material object, then I could not remember "it," because there are no stones in my brain. Nor does it make sense to assert that after kicking "the" stone, I retain an "image" of the stone. Such an image would have to relate to the stone I kicked, and in order to account for this relationship we are forced into infinite regression. The radical realism of phenomenology consists in admitting that the stone I kick is the very same stone I remember. It is neither a material object nor an imprint in my brain. It is an item that has an identity.

--Gian-Carlo Rota

The world is given to me only once, not one existing and one perceived. Subject and object are only one. The barrier between them cannot be said to have broken down as a result of recent experience in the physical sciences, for this barrier does not exist.

--Erwin Schrödinger