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| The divine comedy|
Last Thursdayism (alternately Last Tuesdayism or Last Wednesdayism) is the idea that the universe was created last Thursday, but with the physical appearance of being billions of years old. It's also a counter to the creationism theory. Under Last Thursdayism, books, fossils, light already on the way from distant stars, and literally everything (including your memories of the time before last Thursday) were all formed at the time of creation (last Thursday) in a state such that they appear much older.
Last Thursdayism functions both as a philosophical point on how our observations may not match with "reality" and a reductio ad absurdum of the young-Earth creationist idea of omphalism: if the world was created 6,000 years ago with the appearance of being made billions of years ago, what is there to stop us from claiming it was made Last Thursday?
The debate on whether Last Thursdayism is true has raged on ever since the creation of the universe last Thursday.
“”Last Thursdayism is false because I clearly remember events from before Last Thursday. It does not follow that God could have fixed our minds and experiences to make us think we only felt things before last Thursday. For example I have a note with the date on it, "Wednesday, July 15, 2009." This would not be possible if the world was created on "Thursday July 16, 2009."
The flaw easily shows in the above argument: if God placed your memories of events before Last Thursday into your mind, then it would appear as if you remembered something "before" Last Thursday. Because Last Thursdayism can explain anything, it operates as an unfalsifiable hypothesis (much like the omphalos hypothesis itself).
One can regard Last Thursdayism (and any similar idea) as "hyperomphalisms" - extreme forms of omphalist doctrine designed to show the absurdity of it. As such they constitute a skeptical hypothesis of the very existence of "the past", not just of events that allegedly occured within it.
However, the assumption that all of the universe was specially created is unnecessarily complex (given you have all the evidence for an old universe PLUS the assumption that it was deceitfully created to look old); it thus makes more sense, via Occam's Razor, to assume uniformitarianism and an old universe.
Bertrand Russell explained in 1921 the problems with proving that the universe was created, intact, at a set point in the past in his "five minute hypothesis":
“”There is no logical impossibility in the hypothesis that the world sprang into being five minutes ago, exactly as it then was, with a population that "remembered" a wholly unreal past. There is no logically necessary connection between events at different times; therefore nothing that is happening now or will happen in the future can disprove the hypothesis that the world began five minutes ago.
|—Bertrand Russell, The Analysis of Mind, 1921, pp. 159–60) |
“”As everyone knows, it was predicted that the world would end last Wednesday at 10:00 PST. Since there appears to be a world in existence now, the entire universe must therefore have been recreated, complete with an apparent "history", last *Thursday*. QED.
It gradually gained popularity; on August 25, 1996, the "Church of Last Thursday FAQ" (an early version of "The Last Thursday Catechism") was posted to talk.origins by Michael Keane. This version is similar to Unicornism or Pastafarianism, and claims that the universe was created Last Thursday by "Queen Maeve the Housecat", who on Next Thursday (Judgment Day) will admit those who were nice to cats to Paradise and damn the unkind, the uncaring, and Creationists to the never-cleaned Eternal Litterbox.
In some circles, especially talk.origins, Last Tuesdayism is taken as a schism of Last Thursdayism and is founded on the belief that the world was created last Tuesday — but, unlike last Thursdayism, this happens every Tuesday.
“”We, the Last Thursdayists, followers of Last Thursdayism, members of The Church of Last Thursday, believe:
- Current age of the universe
- Study: All Of Your Memories [Were] Implanted In You 5 Minutes Ago When Universe Was Created (the Onion)
- See the Wikipedia article on Last Thursdayism.
- Last Thursdayism, Wiktionary
- Freethought and Rationalism discussion board - 
- Specifically, by the Dami Mission in South Korea.
- The Church of Last Thursday