Concentration is just the opposite of meditation and so is contemplation, in a different way. Concentration means closing your mind, focusing your mind, on a certain point, on a certain object. You are so focused on a certain object that you become unaware of everything else; that is concentration. It excludes everything else; it includes only one thing: the object of your concentration, whatsoever it is. And meditation means absolute openness. It includes all, it excludes nothing. Hence it is not concentration at all. It is a state of vulnerability, openness, availability.