 There were three main types of semantic analogy, each based on a type of metaphysical analogy. In the original Greek sense, analogy involved a comparison of two proportions or relations. Thus ‘principle’ was said to be an analogical term when said of a point and a spring of water because a point is related to a line as a spring is related to a river. This type of analogy came to be called the analogy of proportionality. In the second sense, analogy involved a relation between two things, of which one is primary and the other secondary. Thus ‘healthy’ was said to be an analogical term when said of a dog and its food because while the dog has health in the primary sense, its food is healthy only secondarily as contributing to or causing the health of the dog. This second type of analogy became known as the analogy of attribution, and its special mark was being said in a prior and a posterior sense (per prius et posterius). A third type of analogy, sometimes used by theologians, appealed to a relation of likeness between God and creatures. Creatures are called good or just because their goodness or justice imitates or reflects the goodness or justice of God. This type of analogy was called the analogy of imitation or participation. Of the three types, it is the analogy of attribution that is central to medieval discussions.