The issue of the union between soul and body presents itself in the Leibnizian philosophy in an unique way through the modern philosophy tradition. Instead of explaining how this relationship happens, Leibniz inquires why does it happen. Through the understanding of the individual substance or Monad as being at the same time logical subject and ontological expressive center, it will be possible to understand why the fashion of how soul and body communicate with each other becomes a question of little or none importance. Through the intertwining of the concept of pre-established harmony with that of expression the German philosopher definitely eliminates the possibility of a causal relationship between both and introduces instead an analogic...