Zoomorphic creatures in Celtic design are stylized and represent belief in the unity of all life.  Within the circle are mnemonic lessons in both duality and triplication.  To the Celt, every aspect of life was a balance between the dualities of male/female, light/darkness, Yin/Yang/ negative/positive.  William Blake, a modern day druid, captured the essence of the belief in the lines "Without contraries is no progression."