Lewis continues his examination by exploring the nature of pleasure, distinguishing Need-pleasures (such as water for the thirsty) from Pleasures of Appreciation, such as the love of nature.[5] From the latter, he developed what he called "a third element in love ... Appreciative love",[6] to go along with Need-love and Gift-love.
Throughout the rest of the book, Lewis goes on to counterpoint that three-fold, qualitative distinction against the four broad types of loves indicated in his title.[7]
In his remaining four chapters, Lewis treats love under four categories ("the highest does not stand without the lowest"), based in part on the four Greek words for love: affection, friendship, eros, and charity. Lewis states that just as Lucifer (a former archangel) perverted himself by pride and fell into depravity, so too can love – commonly held to be the arch-emotion – become corrupt by presuming itself to be what it is not.
A fictional treatment of these loves is the main theme of Lewis's novel Till We Have Faces.
