A kitten is chiefly remarkable for rushing about like mad at nothing whatever, and generally stopping before it gets there.

Repplier’s line is a wry, affectionate observation of kitten behavior—sudden bursts of energy, frantic dashes, and abrupt halts prompted by stimuli invisible to human observers. The humor comes from treating this as the kitten’s “chiefly remarkable” trait, as if it were a defining philosophical characteristic rather than ordinary play. Implicitly, the remark also satirizes purposeless human bustle: rushing “like mad” toward vague aims, then stopping short before any real destination is reached. The sentence’s neat logic (“at nothing whatever… before it gets there”) turns chaos into a mock-rational pattern, capturing both the charm of kittens and the comedy of misdirected momentum.