In the arithmetic of love, one plus one equals everything, and two minus one equals nothing.

Mignon McLaughlin was best known for compact, epigrammatic observations about love and marriage that circulated widely in mid‑20th‑century American newspapers and in her aphorism collections. This line is typically encountered as a standalone maxim rather than as dialogue from a novel or a speech, reflecting her characteristic style: a witty “reframing” of everyday experience through a borrowed structure (here, arithmetic). While it is strongly associated with McLaughlin in quotation anthologies, the precise first publication venue is often not supplied in popular reprints, suggesting it likely entered circulation through one of her compiled books of sayings or syndicated columns.

The quote uses the language of arithmetic to describe emotional reality. “One plus one equals everything” suggests that in love, two people together create a whole that feels larger than the sum of its parts—shared meaning, identity, and a sense of completeness. “Two minus one equals nothing” captures the devastation of loss or separation: when a partnership has become the center of one’s world, subtracting one person can make what remains feel empty. The wit lies in the mismatch between cold calculation and intimate feeling, underscoring how love obeys its own logic rather than rational measurement.