... a society which praises its philosophers and looks down on its plumbers is in for trouble. (Para. 15)
Meaning: ... a society which values its philosophers whether they are good or not and does not value its excellent plumbers will certainly have trouble.
philosopher: n. a person who studies the nature and being of existing, what is real, morals, etc.
To a society both philosophers and plumbers are important. 对一个社会来说，哲学家和管道工同样重要。
be in for: unable to escape; sure to get or have
The weather report says we are in for a storm. 天气预报说将会有风暴。