The initial phenomena of the psychoses are frequently marked by transformations in subjective experience, phenomena that have constituted the object of particular attention in phenomenological psychiatry. Today, however, these experiences are finding themselves playing a significant role in certain neuro-cognitive models of delusion and of schizophrenia. We will be suggesting that these forms of inaugural psychotic experience should be approached as a privileged interface between phenomenological descriptions of presence in the world; hypotheses concerning possible perceptual alterations at the base of these experiences; and the clinical and psycho-dynamic dimension of a specific mode of vacillation or loss of contact with reality.