This is the only single element unduplicated in the brain, without a mirrored partner. Though still much needs to be learned about this mysterious organ, we do know it regulates the function of all the endocrine organs through the hormone melatonin. It has often been referred to as the "third eye" or the bridge from physical to spiritual reality. It is is considered by some to be the physical location for psychic phenomena such as mental telepathy. The 17th Century French philosopher Rene Descartes considered the pineal gland to be responsible for consciousness and soul.