The Power of Sympathy

The father in law uses the analogy comparing the human mind to an extensive plain:

'' When, therefore, knowledge flows on in its proper channel, this extensive and valuable field, the mind, instead of being covered with stagnant waters, is cultivated to the utmost advantage, and blooms luxuriantly into a general efflores cense- for a river property restricted by high banks, is necessarily progressive''.

In your own words, what do you think the old gentlemen means by using this analogy?