Materia Medica is a Latin term that stands for any material or substance used in the composition of curative agents in medicine.

The use of all Materia Medica, or medicine, is historically quackery based upon a myth as old as mankind that medicines possess magical curative powers. In other words, the original mode of action or mechanism for all Materia Medica was magic.

Historically, ancient peoples believed in a benevolent god who would not make people intentionally sick and suffer. Thus, these folk healers among the peasantry population believed in the law of signatures. The law of signatures identified which herbs would be effective against which diseases. By a process of trial and error Western folk healers learned which herbs worked and which herbs did not work.

Materia Medica eventually developed along three different approaches.