This is one of those timeless songs that has had different meanings at various times of my life.
All In Love Is Fair is from Stevie Wonder's Grammy Award Winning album, Innervisions, which won Album of the Year in 1974. The lyrics, composition and production were the work of Stevie Wonder, a musical genius despite being born blind.
The song has been commercially successful covered by Michael McDonald and Barbra Steisand, among others. My favorite version remains the original by Stevie Wonder.