Although surrealism appeared in Europe at the beginning of the 20th century, manifesting especially in the 1920's and 1930's, its antecedents date from much earlier. A good example of of "surreality", "over-reality" or "superior reality" that its defenders already tried to capture and reflect can be found in the 5th century BC. Based on the famous assertion assigned to Heraclitus, the difference between vigil and sleep, and in general between any kind of opposites, is only apparent: "Being alive and dead, awaken or asleep, being young and old: all of it exists at the same time within us". The prominence of imagination, of dreams and visions, of the emotional world commonly represented in monstrous and ghostly images, which the surrealists claimed, can already be observed in some artists of the Middle Ages and the Renaissance like for example Brueghel or Bosch. These artists, would at the same time inspire many representatives of romanticism, establishing this way a chain of successive influences that the own surrealist would accept as the precedents of their movement.