Sympathetic magic is a specific magical paranormal belief that similar objects affect each other. (This concept is often phrased as "like affects like," as in homeopathy.) Anthropologically speaking, this is apparently one of the most common and most primitive forms of magical belief, found in communities and cultures all over the world.
For thousands of years ago it was known to the sorcerers of ancient India, Babylon, and Egypt, as well as of Greece and Rome, and at this day it is still resorted to by cunning and malignant savages in Australia, Africa, and Scotland. Thus the North American Indians, we are told, believe that by drawing the figure of a person in sand, ashes, or clay, or by considering any object as his body, and then pricking it with a sharp stick or doing it any other injury, they inflict a corresponding injury on the person represented. For example, when an Ojebway Indian desires to work evil on any one, he makes a little wooden image of his enemy and runs a needle into its head or heart, or he shoots an arrow into it, believing that wherever the needle pierces or the arrow strikes the image, his foe will the same instant be seized with a sharp pain in the corresponding part of his body; but if he intends to kill the person outright, he burns or buries the puppet, uttering certain magic words as he does so. The Peruvian Indians molded images of fat mixed with grain to imitate the persons whom they disliked or feared, and then burned the effigy on the road where the intended victim was to pass. This they called "burning his soul."
In alternative medicine, sympathetic magic is often presented under the guise of the Doctrine of signatures, the idea that everything is "marked" in some way with a signature or guide to its intended use. For example, a plant with an arrow-shaped leaf might be a good treatment for arrow wounds. Plants with yellow sap would be jaundice treatments, and plants and animals with long lives could be used to extend human life. More formally, the plant Hepatica acutiloba better known as liverwort ship has leaves that look somewhat like a human liver, and is therefore believed by some herbalists to have a beneficial effect on liver complaints.
Scientific investigation has produced no support for the idea that sympathetic magic applies to the natural world. Nevertheless, the tendency to believe in sympathetic magic has been used to good effect in artificial environments. The Graphical User Interface, in which a user manipulates a symbolic representation of an underlying structure, resulting in changes to that structure, can be considered a form of artificial sympathetic magic. Few people understand computer software, and even fewer also understand computer hardware, so the workings of a computer might as well be considered magical. Under Clarke's Third Law, "any sufficiently advanced technology is indistinguishable from magic". Even seasoned professionals use the term "Fancy Magic" to describe mysterious aspects of a system, although another word with the same first letter is usually substituted for "Fancy." As most ancient and isolated peoples have expressed, the forces of magic can be capricious, arbitrary, mendacious, and cruel. People who use modern software also find this true.