The session and its continuum in everyday life must of course be considered as a third-party relation; in it, « two people looking at each other » are brought together and compromised under the same «other» gaze ; a group is formed, trust (and illusion) shared… The lighthouse, initially unknown (a stranger), inspires exchanges that are more and more familiar: talking replaces being looked at. Thanks to this third-party construction, the interactions that define the site can henceforth be interpreted or « reconstructed ».