In several threads the subject of existence arises. What do we define as 'existence' and what kind of existence can we recognize? First and foremost we should recognize that existence in the real sense (something that exists outside of our mind, has existence on it's own) is material existence. It has the basic properties of movement/change (all existence requires it to change/move in time), and it is therefore existence in a spatiotemporal way. On the other hand we can recognize another category of existence, which is ultimately dependend on the mind itself. The set of numbers or geometrical shapes, etc., belong to this category.