This is from a response I wrote to a question on an email group.
Do Wiccans and neopagan witches have familiars? It really depends on who you ask. There are plenty of people that will say that a familiar is an animal who is bonded in some way with the witch and that helps them with their magic. Familiars are often beloved pets, are said to choose the witch, and seem drawn to magical workings (http://www.netplaces.com/wicca-witchcraft/the-animal-kingdom/familiars.htm). It seems like everyone has a familiar these days and people will talk about theirs with little reason to - and show pictures. New witches will wring their hands and worry about why they don't have one and how to get one, and be offered sage advice from those who do claim to have them. Familiars are a hot commodity.
In all honesty I am in the other camp, which is the minority; I do not believe that familiars exist in the sense of pets we bond with. The idea of familiars is medieval, based on accusations that "witches" were assigned a demon to serve them and that this demon took the form of a common animal to blend in - the word familiar itself is shortened from familiar spirit, as in "she hath a familiar spirit". Obviously since Wiccans don't make pacts with the Christian Devil or work with demons they don't have familiar spirits, ergo no familiars. There is a secondary approach that views familiars as faeries that attach themselves in animal form to specific people, especially those who practice cunning craft or are closely allied with the Fey, but this concept is not as well known or widespread and would apply on in very specific cases. In either case the historic views of what a familiar was are not often understood in a modern context.
The modern idea tends to focus on familiars as closely bonded pets who are sensitive to magic workings, but historically a familiar would actually be used for a variety of magical purposes such as carrying messages, enhancing magic, delivering spells to their targets etc.,, effectively making the animal a source of magical energy and an energetic servant. How many of us actually want to use our beloved pet as a magical battery? Others will argue that a familiar is an animal that is not a normal animal but has a special spirit, sometimes even the spirit of a person or guide within it. Do you really want to believe your cat is possessed or overshadowed by a secondary spirit? Because the alternative is to believe that the spirit has permanently bound itself into flesh for the lifetime of the animal which is very limiting to the spirit and would reduce its ability to effectively guide you.
To me it seems like some people who are very very close to a particular pet choose to view that pet as a "familiar" because it sounds special and important, not because the pet is actually serving the traditional role of a familiar. I would not want my cats to "serve" me magically, or to be possessed, or to be anything but happy kitties living happy kitty lives; maybe that's my bias showing ; ) I do think there may be certain cases where an animal actually is a familiar or at the least is bonded to the person in a way that is genuinely unusual, but I think these cases are far less common than the ones that are just pets. And there's nothing wrong with that. I can love my pets as they are without needing them to be anything but pets.
Davies, O., (2003). Cunning-Folk: Popular Magic in English History. London: Hambledon Continuum.Thomas, K., (1973). Religion and the Decline of Magic: Studies in Popular Beliefs in Sixteenth and Seventeenth Century England. London: Penguin.
Wilby, E., (2005). Cunning Folk and Familiar Spirits: Shamanistic Visionary Traditions in Early Modern British Witchcraft and Magic. Brighton: Sussex Academic Press.
Massello, R., (1996). Raising Hell: A Concise History of the Black Arts and Those Who Dared to Practice Them. Perigee Trade