"the happy region of the Three Dimensions'

From "Flatland" by Edwin Abbott Abbott

You, who are blessed with shade as well as light, you, who are gifted with two eyes, endowed with a knowledge of perspective, and charmed with the enjoyment of various colours, you, who can actually SEE an angle, and contemplate the complete circumference of a Circle in the happy region of the Three Dimensions-- how shall I make it clear to you the extreme difficulty which we in Flatland experience in recognizing one another's configuration?

"Flatland" is free online.