How did liver divination seek to discover the will of the gods?

In ancient Mesopotamia, liver divination—known as hepatoscopy—was a primary method used to seek direct answers from the gods regarding their will or intentions.1

The practice involved the following elements:

• Sacrificial Context: A lamb or kid was sacrificed specifically for divinatory purposes. The liver was considered the vital center of the animal, rather than the heart.12
• Reading the Signs: Diviners examined the liver to interpret variations in its form, shape, and markings, which were believed to be "written" there by the gods.1
• Systematization: By the 2nd and 1st millennia BCE, this practice had become highly structured, with large, detailed handbooks composed to guide diviners in their interpretations.1
• Mapping the Cosmos: The discipline of haruspicy (the study of the liver) involved mapping the organ as a microcosm. The sacrificial altar was viewed as the center of cosmic space, and different sectors of the liver were assigned specific meanings, allowing diviners to chart and ponder divine messages.2

While often used to ascertain the divine will, some evidence suggests the practice may have originated as a way to read "symptoms" of the future, similar to how a physician identifies the onset of a disease.1