Stranger, dreams verily are baffling and unclear of meaning, and in no wise do they find fulfilment in all things for men. For two are the gates of shadowy dreams, and one is fashioned of horn and one of ivory. Those dreams that pass through the gate of sawn ivory deceive men, bringing words that find no fulfilment. But those that come forth through the gate of polished horn bring true issues to pass, when any mortal sees them. But in my case it was not from thence, methinks, that my strange dream came.
- The Odyssey, translation by Arthur T Murray
The gates of horn and ivory are a literary image used to distinguish true dreams from false. The phrase originated in the Greek language, in which the word for horn is similar to that for fulfil and the word for ivory is similar to that for deceive. On the basis of that play on words, true dreams are spoken of as coming through the gates of horn, false dreams as coming through those of ivory.
The horizontal lines in both Ivory and Horn are comprised of an interpretation of the wavelengths representing rapid eye movement whilst asleep (REM). The upper line represents the left eye and lower, the right eye. Lines drawn between the two eyes form the permeable gateways through which dream content is deciphered.