Acorns Or Oak Trees?

I've just finished reading E.F. Schumacher's 'A Guide for the Perplexed', which systematically takes the reader through the different ways of knowing the world and is full of hidden treasures like this.

"Our ordinary mind tries to persuade us that we are nothing but acorns and that our greatest happiness will be to become bigger, fatter, shinier acorns; but that is only of interest to pigs. Our spiritual mind gives us knowledge of something much bigger: that we can become oak trees."