The Argument from Desire
You keep wanting something nothing on Earth delivers. Lewis says that's not a glitch.
Grounded in the research on the argument from desire
Childhood: the stab
C.S. Lewis spent his early life ambushed by a feeling he couldn't name. A toy garden, a line of Norse poetry, autumn light. A sharp pang of longing that vanished the second he reached for it, leaving him wanting the wanting back. He borrowed the German word Sehnsucht and capitalized it as 'Joy.' Not happiness, not pleasure. An unsatisfied desire more desirable than any satisfaction. That ache is the raw data the whole argument runs on.
The pattern he noticed
Lewis chases Joy for decades and keeps misfiling it. He thinks it's sex, or nature, or nostalgia, or the occult. Every time he corners the object, the Joy is already gone, pointing past it. He clocks the pattern: natural appetites have real targets. A baby's hunger means food exists. A duckling's urge to swim means water exists. So what does an appetite with no earthly object mean? That question becomes the argument.