Based upon two principles. First, "like produces like" and that possessions having been in contact with each other continue to react upon one another even after they have been severed. This is the reason that when performing a spell the practitioner may have in her or his possession something personal of the intended, such as a lock of hair, nail clippings, a piece of clothing, or a photograph. Examples include the possession of an Icon, Crucifix, Sacred Book, Soil, Herb or remains of the intended.
An item transfers the effect of the Magickian's actions on the person who once was in contact with it. This thing possesses an occult empathy that exists between the object and person. This empathy or sympathy is an impulse being transmitted from one thing to the other by means of ether, not unlike that which is hypothesized by modern science for a similar purpose, namely, to explain how things can physically affect each other through space.
One example of Sympathetic Magick is the Witch's Ladder. 40 knots are tied tightly in a cord with a concentration of fierce hatred against the victim. Then the cord is hidden so the intended person could not find it -because the only way to break the spell is to untie the knots -the knots strangled the life out of the person until he untied them all.
One frequently hears the phrase burned in effigy, which means to let it be known publicly that a person is hated and his enemies want to destroy him. The history of this spectacle reaches back for thousands of years. Occurrences of it were found in ancient India, Babylon, Egypt, Greece and Rome. The idea of burning in effigy is pure Sympathetic Magick: just as the image suffers, so does the man.
Poppet (or Doll) Magick is another use of Sympathetic Magick. It is the reverse of burning in effigy. Instead of desiring to kill or injure the person whom the poppet represents the practitioner wishes to help him. The theory is whatever degree of healing the practitioner performs on the poppet; the same degree of healing is believed to occur in the person that the poppet represents. So it can be seen that those who subscribe to and practice puppet healing do believe that Sympathetic Magick can produce positive affects.