Throughout the book, Galileo reiterates his opinion that few have a true understanding of nature and reality—and that they are far outnumbered by those who merely follow fashionable opinions or make rash and superficial judgments not based in reason. As he states in the “Letter to the Grand Duchess Christina,” “[p]eople who are unable to understand perfectly both the Bible and the sciences far outnumber those who do understand” (190). This is because seeking true knowledge takes time and effort, which most people are not willing to invest. As Galileo puts it: “It is much more pleasant to gain a reputation for wisdom without effort or study than to consume oneself tirelessly in the most laborious disciplines” (190).

Again, in “The Assayer,” Galileo remarks to Sarsi that “good philosophers […] fly alone, like eagles, and not in flocks like starlings” (239). This implies that to be a sound thinker, one must be independent and not follow the crowd. Galileo is implicitly referring to many of his critics, whom he accuses of being superficial thinkers who cherry-pick biblical quotes without understanding their meaning. These critics ganged up on Galileo to try to destroy him, without even understanding his arguments. Galileo again emphasizes the rarity of true knowledge in addressing Sarsi, stating that “the crowd of fools who know nothing, Sarsi, is infinite.