This is the text of a lecture which was given by Marco De Marinis at the 3rd International Conference on Theatre Anthropology, "Odin Teatret and Theatre Anthropology in Greece", 17 and 18 March 2023. The conference was organised by: Theatre Laboratory of Drama and Speech Department of Theatre Studies; Co-organisers: Centre of Theatre Anthropology, Heraklion-Crete, Fondazione Barba Varley, University of Patras, Science and Technology Museum. De Marinis's speech highlights parallels and complementarities between the notion of Third Theatre, Theatre Anthropology and the genesis of ISTA, establishing that Barba's writings relating to Third Theatre address the issues of "why" and "for whom" theatre is done, while those relating to theatre anthropology question the "how", and therefore the techniques. Furthermore, the Italian scholar defines theatre anthropology as a discovery deriving from the work carried out by directors-pedagogues during the 20th century and from the work of actors who, at a pre-expressive level, do not learn to interpret or act but build their stage presence. Finally, after having defined the extra-daily techniques as those that the actor applies to put in practice the pre-expressive principles, De Marinis outlines three lessons that he learned by participating over twenty years in several ISTA sessions.