Matthew Yglesias proposes that we “assume that God created the universe—fossils and all—to look exactly like that 4,000 years ago. That’s obviously a religious hypothesis rather than a scientific one, but it’s consistent with the evidence and doesn’t anyone to believe in a scientists’ conspiracy or anything.”
This assumption is OK as far as philosophy goes, but it misses a crucial detail: if God did create the universe in this fashion, why should I care? Young-Earth Creationism, at least in its American Christian incarnation, is not simply an allegation of facts about the universe. It casts the scientific view of the world’s origins as not merely incorrect but evil, because it implies a history of progress1 without intervention from a personal God. By contrast, in this ideology, the earth is not merely six-thousand-ish years old, but bears a six-thousand-year history of paradise, decline, and redemption.
1 To see evolution as “progress” from “lower” to “higher” forms of life is a mistake going back to the Victorians, but young-earth creationists are not the only ones unclear on that concept. A co-worker of mine once reported hearing, from a certain world-famous linguist, that the syntax of natural languages must be optimal, because the human capacity for language is the product of evolution. “But… but…”, I sputtered, “evolution only tends to local… maxima…” She rolled her eyes in sympathy.