FIGURE 1.

Prior to the seventeenth century, the experiences we now name hallucinations were valued within a cultural context, they could bring meaning to the subject or the world. From mid-seventeenth and eighteenth centuries, they acquire a medical quality to designate mental and organic illnesses. However, the term is fully integrated in psychiatry by Esquirol in the eighteenth-nineteenth centuries. By then, a controversy begins on whether hallucinations have a perceptual or intellectual origin. Esquirol favors the intellectual origin (involuntary exercise of memory and imagination). Tamburini believes they are the result of the stimulation of the centers of imaging formation in the brain, but Parish advances with a more integrative approach. In the twentieth century, some authors maintain that hallucinations are a form of delusion (Ey), while others describe it as a change in perception (Jaspers, Fish). A more integrated perspective, like the one proposed by Alonso Fernandez and Luque, highlights the heterogeneity of hallucinations and the multiplicity of their types and causes, even within hallucinations with a psychiatric (and non-organic) cause. Multiple explanatory models were also developed during the twentieth century.