This is a very interesting question. Although many people have discussed it, there hasn’t been a conclusive answer because there hasn’t been a detailed series of studies specifically for this question. Therefore, there are several different explanations:
- The first explanation suggests that when a donkey pushes a millstone, it covers its eyes to prevent its attention from wandering and to avoid becoming lazy and stopping pushing the millstone after a while.
- The second explanation posits that when a donkey pushes a millstone, if it doesn’t cover its eyes, it may smell the food aroma and see food on the millstone, which might tempt it to stop and eat what’s on the millstone. Thus, covering its eyes helps it to keep pushing the millstone without distractions.
- The third explanation suggests that as a donkey pushes the millstone continuously in one direction, what its eyes see is also rotating in the opposite direction. Over time, this rotational motion could make the donkey feel dizzy or uncomfortable, similar to how humans might feel dizzy if they spin around with their eyes open. Covering its eyes prevents the donkey from sensing this rotational motion, allowing it to push the millstone for longer periods comfortably.
- The fourth explanation proposes that different donkeys may exhibit different behaviors, possibly combining two or more of the above reasons, or possibly all three factors affecting each donkey’s behavior when pushing a millstone.
These explanations are speculative and based on individual observations. The true reason can only be determined through careful and detailed investigation and study of donkeys pushing millstones under various conditions.