I assume you have made a mistake, the word '自' has non sense in the context, commonly it should be instead by '白'.
Here is my translation:
-- Men when eating, they can be grouped in three categories:
-- Which ones？
-- Man can eat something by himself depending on his competence.
-- Man can't eat something by himself because he don't have the competence, and man can eat something without understanding why he can, more like of wasting what he have eaten.
These words contain a lot of metaphors, it must be comprehended by the environment.
Hope this can help you.