Chronological snobbery

Chronological snobbery, a term coined by friends C. S. Lewis and Owen Barfield, is a logical argument (and usually when thus termed, considered an outright fallacy) describing the erroneous argument that the thinking, art, or science of an earlier time is inherently inferior when compared to that of the present. As Barfield explains it, it is the belief that "intellectually, humanity languished for countless generations in the most childish errors on all sorts of crucial subjects, until it was redeemed by some simple scientific dictum of the last century." The subject came up between them when Barfield had converted to Anthroposophy and was persuading Lewis (an atheist at that time) to join him. One of Lewis's objections was that religion was simply outdated, and in Surprised by Joy (chapter 13, p. 207-208) he describes how this was fallacious:

Barfield never made me an Anthroposophist, but his counterattacks destroyed forever two elements in my own thought. In the first place he made short work of what I have called my "chronological snobbery," the uncritical acceptance of the intellectual climate common to our own age and the assumption that whatever has gone out of date is on that account discredited. You must find why it went out of date. Was it ever refuted (and if so by whom, where, and how conclusively) or did it merely die away as fashions do? If the latter, this tells us nothing about its truth or falsehood. From seeing this, one passes to the realization that our own age is also "a period," and certainly has, like all periods, its own characteristic illusions. They are likeliest to lurk in those widespread assumptions which are so ingrained in the age that no one dares to attack or feels it necessary to defend them.

Pattern
The form of the chronological snobbery fallacy can be expressed as follows:
 * 1) It is argued that A implies B.
 * 2) A implies B is an old argument, dating back to the times when people also believed C.
 * 3) C is clearly false.
 * 4) Therefore, A does not imply B.

Examples
C. S. Lewis in Surprised by Joy (Chapter 13, p. 206) recounts his story: First Harwood (still without changing his expression), and then Barfield, embraced the doctrines of Steiner and became anthroposophists. I was hideously shocked. Everything I had labored so hard to expel from my own life seemed to have flared up and met me in my best friends. Not only my best friends but those whom I would have thought safest; the one so immovable, the other brought up in a free-thinking family and so immune from all "superstition" that he had hardly heard of Christianity itself until he went to school. (The gospel first broke on Barfield in the form of a dictated list of Parables Peculiar to St. Matthew.) Not only in my seeming-safest friends but at a moment when we all had most need to stand together. And as I came to learn (so far as I ever have learned) what Steiner thought, my horror turned into disgust and resentment. For here, apparently, were all the abominations; none more abominable than those which had once attracted me. Here were gods, spirits, afterlife and pre-existence, initiates, occult knowledge, meditation. "Why–damn it–it's medieval," I exclaimed; for I still had all the chronological snobbery of my period and used the names of the earlier periods as terms of abuse.

The usage in general of the word "medieval" to mean "backwards" is also an example -- as is the use of the term "backwards" to mean "unsophisticated."

G. B. Tennyson in his book Owen Barfield: Man and Meaning offers the following firsthand account: I was attending a lecture with a varied but exclusively university-oriented audience of some five hundred when the lecturer, a Ph.D. in physics, said, almost in passing, "Remember that only three hundred years ago men actually believed the world was flat!" Considerable knowing laughter greeted this astonishing misrepresentation (or, should I say, falsehood?), and the assembled all murmured a kind of self-congratulatory hum of satisfaction with their own superior knowledge. At another point the lecturer dropped a reference to the onetime belief that the sun revolved around the earth. More laughter. The physicist, it was apparent, was merely offering burnt incense at the altar of some of our twentieth-century idols.