Quote from : The Adolescent Book

Sincere and unspiteful laughter is mirth, but where is there any mirth in our time, and do people know how to be mirthful?... A man's mirth is a feature that gives away the whole man, from head to foot. Someone's character won't be cracked for a long time then the man bursts out laughing somehow quite sincerely, and his whole character suddenly opens up as if on the flat of your hand. Only a man of the loftiest and happiest development knows how to be mirthful infectiously, that is, irresistibly and goodheartedly. I'm not speaking of his mental development, but of his character, of the whole man. And so, if you want to discern a man and know his soul, you must look, not at how he keeps silent, or how he speaks, or how we weeps, or even how he is stirred by the noblest ideas, but you had better look at him when he laughs. If a man has a good laugh, it means he's a good man.