How do we know that we are real and that we actually exist? Sure, we can look at ourselves in the mirror, pinch ourselves or bang our heads against the wall, But even that, could just be something that we imagine. However, how are we able to imagine something, if we don't exist? And that's how we get to the crux of the matter: When we question reality, if what we are seeing is real or not, there is always us. That isn't up for discussion. But how can we be certain of our existence? Precisely: To be or not be, that is the question here! The concept of `being' has the broadest definition by far, because it relates to everything conceivable. To our house, our boat, our investment advisor and, of course, ourselves! "Everything that is conceivable," therefore also means: everything that "is not" isn't. And all of that combined is infinite! Boldly stated: nothing exists outside of being, as everything that exists is part of being. But that is only half the battle Because being isn't equal to existence. In the Middle Ages, "existence" was distinguished into that which was essential which was the "necessary existence". That which was essential for everyone and everything was the basis for everything that existed, and was naturally called God. There where the necessary exists, the unnecessary doesn't seem far away. Thus the 2nd kind of the existence was defined as "not necessary"... simply things which nobody needs! USB ashtrays, inflatable cell phone holders, breakfast egg heads, pasta in a cooking bag, microwave slippers.... okay. Apart from that which no one needs, there is also the existence of that which can be almost impossible: the "impossible existence". Does that mean that God is unable to create a rock that he himself cannot lift!!! Then how can something exist that is more powerful than the necessary existence? Kant then proposed sensuality and experience... his sources of understanding! Should that then mean, that things appear to exist, because of the way we experience them. His colleague Hegel saw it like this: The unity of essence and appearance, of essence and existence is reality. So, the essence must appear, then the being is essence and the essence is being.... Uh…Wait a moment So, to summarise: the essence of being is essential being. Plain and simple, the existence. Kierkegaard saw it differently yet again and thus became the founder of the philosophy of existence: "Being itself, to which the mode of being can behave in a particular way and always behaves in one way or another, we call existence". By this he means that this existence is quite sufficient. It relates only to itself and not to a great absolute. I am myself and I am responsible for getting along with my own self. What else is …., I don't care! So much to existence. And to not exists at all? Martin Walser once said: "Nothing is true without its opposite" Whoa! So, it's that simple then.