Sympathetic magic is based on the metaphysical belief that like affects like. Sympathetic magic is the basis for most forms of divination. The lines, shapes and patterns in entrails, stars, thrown dirt, folded paper, the palm of the hand (the longer the lifeline, the longer the life), etc., are believed to be magically connected to the empirical world--past, present and future. It is also the basis for such practices as sticking needles into figurines representing enemies, as is done in voodoo. The pins and needles stuck in a doll are supposed to magically cause pain and suffering in the person the doll represents.
Sympathetic magic is the basis for psychometry, the claim of psychic detectives that touching an item belonging to a victim gives magical contact with the victim. Barry Beyerstein believes that sympathetic magic is the basis for many New Age notions such as "resonance," the idea that if things can be mentally associated they can magically influence each other. Beyerstein also explains many notions of graphologists as little more than sympathetic magic, e.g., the notion that leaving wide spaces between letters indicates a proneness to isolation and loneliness because the wide spaces indicate someone who does not mix easily and is uncomfortable with closeness. One graphologist claims that a person betrays his sadistic nature if he crosses his t's with lines that look like whips.
Sympathetic magic is probably the basis for such notions as karma, synchronicity, eating the heart of a brave but defeated warrior foe, throwing spears at painted animals on cave walls, wearing the reindeer's antlers before the hunt, having rape rituals to increase the fertility of the crops, or taking Holy Communion to infuse the participant with Divinity. Sympathetic magic is surely the basis for homeopathy and remote healing.
Anthropologists consider magical thinking a precursor to scientific thinking. It is indicative of a concern with control over nature through understanding cause and effect. Nevertheless, the methods of magic, however empirical, are not scientific. Such thinking may seem charming when done by our ancestors living thousands of years ago, but today such thinking may indicate a profound ignorance or indifference towards science and a testable understanding of the world. Most of us, from time to time, undoubtedly slip into this primitive mode of thinking, but a bit of reflection should wake us up to the fact that oysters are not an aphrodisiac, having a bit of good luck is not likely to influence our chances of winning the lottery that day, and stabbing a photo of an enemy is not going to hurt her. It may be true that rubbing an amulet given you by your true love makes you feel her presence, but the feeling you have, however magical it may seem, has more to do with biology and psychology than with metaphysics.
Source