There is a theory that says that the world is illusion, "maya", and that we create the whole of reality within our own minds. This is heard often in the New Age arena, and such philosophies are initially very attractive for they feed the ego of the newly expanded mind. If you mind can be stretched to encompass more than you ever realised before then why stop at the boundaries of the known universe - why not have created everything yourself?
This philosophy is very attractive at first glance, but with a little contemplation it unravels in a sea of ego. We do not create the whole of reality in our minds. When we have psychedelic or other transcendent experiences we can fall prey to the idea that we are being shown that we ARE the whole of reality and it is unfolding within us. We are not such a beast. Instead, we are involved and part of anything that we put our attention upon. That would be a more accurate statement. From that perspective you can see that within your perception of the world at any particular time it could appear that you are part of everything. You are not. You are only part of everything that you perceive with all of your senses.
It is pure ego which is imagining that it is part of everything. Think about it - 'everything' is a whole lot of stuff. You are not part of everything. You are only part of that which you move your attention - whether physical attention or spiritual attention - to focus upon.