When we are asleep we generally experience two conditions: the dream and the deep sleep. The dream is the uncontrolled activity of the mind. When we are awake, when our mind works without control, it shows us pictures which come from its store of impressions and we call this imagination. When we control the activity of the mind we call it thought. The imaginings that come during sleep we call dreams. We do not call them real, because our waking state shows us something different; but while we are not in the waking state the dream is real.