This is a talk / a paper where I try to answer the fundamental question What is it ?
What is the sky? What is inspiration? What is the number Pi ? What is democracy? And so on...
How to answer this kind of basic question ? Is there a methodology ? Do we need to use differents ways according the topic, the x of the question?
This question is a fundamental question which was put forward by Socrates and Plato and which includes other questions such as How ? Why ? When ? Where ?