Within the fabric of creation is the internal construct. Often described by Angels as being similar to HTML, creation is divided between what you can see and physically interact with (the Material) and what you can't (Fabric and Divine Forces). In between these are worlds known as Layers (Planes and Realms).
When a magic user uses magic to alter reality, they are altering the Divine Fabric. Although these changes are only temporary, the magic user defies the programming of creation to create an effect that is not natural and does not follow the code. As a result, a Paradox may occur. Of the most famous Paradox's to occur is Deja Vu, others may occur such as forgetting handfuls of time or Quiet.