In the irregular XV, XVI and XVII centuries objects seemed to escape themselves, uncertain of their own identities, and this is why their universe was governed by the spiral of metamorphosis, the mirror of anamorphosis, the crystal of Sosia, the mist of the spectre and the soil of the shadow. During the Renaissance, as well as the Mannerist and Baroque periods, discoveries in the field of perspective had a swift influence on the literary imagination and on the way that things and beings were portrayed. In theatre, many problems related to "optical perspective": the verisimilitude and the mimesis, with regard to the dramatic fiction; the concept of the Baroque and the concept of Mannerism, with regard to the aesthetic; in Shakespeare, the optical perspective is related with the problem of the theatrical illusion.