Reality

Reality works based on a subconscious agreement between all creatures that can percieve the reality. Essentially, we all agree that an apple is an apple, whether we know that a specific apple exists. That agreement creates an energetic pressure to keep the apple as an apple.
Reality is a combination of collective unconscious and the Schrodinger principal - that is, observation of an item creates a kind of existance-wide, subconscious buy-in of what the observation is. While certain aspects of that observation can be argued, the basic nature of the item is set.
Changing those set natures of the item is extremely difficult. However, once the item has changed, that new nature becomes the agreed-upon reality.