Explorations in Autism is a turning-point in both the understanding of and the clinical approach to autism. The clinical material gradually unveils the geography of the internal mother (which proved crucial for the development of Meltzer’s ‘claustrum’ theory) and allowed him to draft, for the first time in psychoanalysis, a theory of the dimensionality of mental life. At the same time this sheds a new light on the primitive developmental phases of every human mind, giving substance to fundamental concepts such as primal depression, dismantling, adhesive identity, and dimensionality as an ubiquitous parameter of mental functioning.