To his various accusers:

Of all the types of value judgments, the worst is the vilification of those who have thought too much and too deeply, who have gone beyond the grasp of their accusers. While we experience the pleasures of thought we cause no harm to anyone; unfortunately, there are always some who feel they have taken harm. Honestly, it is not everyone who can feel this kind of pleasure, but we cannot be held responsible for that. I can see no reason for the negation of such pleasures, unless one takes a despicable sort of jealousy into account. There are some in this world who like variety, and some who like simplicity; I have never observed those who love variety to be jealous of those who like simplicity, nor cause them any harm, I have only ever seen the opposite. If I know anything at all about science and art, it is that they are fed equally by the broad river of the pleasure of thought. This river benefits all humankind but it does not, as some imagine, flow for any one of us alone, just as those who take pleasure in thought were not born for anyone but themselves.

From 思维的乐趣 (The Pleasure of Thought), from his collection 我的精神家园 (My Spiritual Homeland).