Literally: many – fork in the road – die – sheep
Alternately: Presented with an overabundance of options or possible paths, one ends up confused and lost. By extension, a field of study being so finely divided that it becomes difficult to discern underlying principles.
Notes: Despite the literal meaning of 亡, the two-character compound 亡羊 actually refers to a sheep getting away from its shepherd and becoming lost. This compound supposedly comes from an allegory told by Warring States period philosopher Yang Zhu, as found in a classical Daoist text known as the Liezi.