What does Bertrand Russell mean when he says that “The value of philosophy is, in fact, to be sought largely in its very uncertainty.

In the Value of Philosophy (Bertrand Russell in Powerful Ideas p. 208) Bertrand Russell outlines the perennial value of philosophy. What does he mean when he says that we must be liberated from the “practical man.”? What does he mean when he says that “The value of philosophy is, in fact, to be sought largely in its very uncertainty. “ 250 words.