Twisted Logic — Eruvin 53a
תלמוד בבלי מסכת עירובין דף נג/א
אמר רבא ואנן כי אצבעתא בקירא לסברא
Rashi explains Rava’s statement as meaning that compared with the Sages of previous generations, our logic is akin to a finger rubbing at hard wax, which cannot penetrate the wax, but only becomes a bit sticky.
The Chasam Sofer gives an alternative explanation (Teshuvos 6:85).
In Avos (5:7), among the seven qualities of a Sage, is enumerated the trait of not being afraid to respond. The Rambam in his commentary there explains the trait, writing that it means that a Sage answers quickly, and does not fear nor tremble before the question. The Sage immediately perceives the questioner's error, can respond on the spot, and does not need to resort to extended consideration.
The Chasam Sofer elaborates: There is no end to pilpulim (obscure argumentation or casuistry). Given enough time, any person can rebut his fellow's position, and vice versa, from sheer love of debate. Consequently, says Rava, we are like a finger in wax — but in soft wax. Just as a person's finger in wax can twist and shape the wax any way he wants, so too the logic of later generations is not strong and firm, for everyone twists their logic to reach their desired conclusion.
On the other hand, what if a person immediately, without extended consideration, finds a retort that refutes the questioner's error? Then, since he did not take the time to twist logic to formulate a rebuttal, we would treat that retort as an accurate interpretation of his previous position before the give and take began.
Earlier generations, however, could retain objectivity throughout a debate. They would not fall prey to the twisting of logic out of love of debate.