The injunction that ‘it should either entirely be, or not be at all’ leads the goddess to a series of inferences about the nature of being which are wholly at odds with the conclusions of Parmenides’ predecessors. For although there might appear to be a similarity between Thales' isolation of water as the substance that the whole world is made of and Parmenides' belief in the singularity of being, the resemblance, as Parmenides wants to show us, is only superficial. Behind Thales' claim that the world is water, or Heraclitus' claims about fire, the implied assumption is that it is water and therefore not air, or fire and therefore not water. In other words, these elements act as relative concepts of being' rather than absolute ones.