Analytical method of knowledge cannot cope with relevant problems, such as individualità, order, regularity- To treat these problems is indeed very promising the systemical approach. An object can be considered as a system whwn it is an organisation, that is to say when it exhibits invariant relationships which bind the behaviour of fluctuating parts (or elements). It is relevant to notice that the system has properties that its parte do not have. The concept of system is interesting for philosophers because it is a new tool of comprehension, already used in the past (for example by Aristotle with the theory of substance) but worth of special reflection.