"[David I. Masson] began publishing sf with "Traveller's Rest" for NEW WORLDS in 1965; his fiction, including this extraordinarily intense study in the distortion of PERCEPTION, was assembled in The Caltraps of Time (coll 1968), which single volume established his strong reputation as a writer of vigorously experimental, vivid, often scientifically sound stories. Notable among them, and reflecting his close and informed interest in LINGUISTICS, were "Not so Certain" (1967) and the brilliant TIME-TRAVEL story "A Two-Timer" (1966), told entirely in language appropriate to 1683, the year from which the inadvertent time traveller is whisked into the future. Each of DIM's stories seems to be a solution to some cognitive or creative problem or challenge ..."
— John Clute, The Encyclopedia of Science Fiction