Wiccans, Pagans and Witches see the Divine as being manifest through the God and Goddess. Our ability to comprehend the universe and the world around us is limited, and viewing the Divine as masculine and feminine aspects of the One Universal power helps us understand this energy a little better. The fact that some call upon or associate with the Divine by different names does not necessarily mean that we see a complete seperation of deities.
We accept that different aspects of the Divine combine to make the whole or One. In this view, we recognize and attune ourselves with nature and the creative force in a way the individual or group is most comfortable with. The following is an explanation of this concept which most agree upon.
The One is the all encompassing unity of all things which exist. This includes that which manifests to our limited awareness and understanding as well as that which is not. The One is infinite to a point that the human mind simply cannot comprehend its vastness.
The Goddess and God are seen as a manifestation of the feminine and masculine forces of nature. Each having unique characteristics that when combined result in the harmonious creation of life.
We see examples of this in everything around us as nothing can exist without the interaction of feminine and masculine energy. This creative energy is omnipresent. They are concepts that allow the human mind to comprehed the creative force of the world around us.
Giving name to the divine or feminine and masculine energies is in many ways irrevalent and certainly cannot justify the wars and bloodshed history has seen because of it. They are simply names humanity, a culture or specific belief system has created over time for association purposes.
It really matters little whether we associate with the divine as the "Father, Son and Holy Ghost" or "The One, Goddess and God." Ultimately, the concept is the same.