I read in an answer somewhere on this site that Modus Ponens involves an infinite regress.
Upon reading Lewis Carroll's Achilles and the tortoise, I fail to see how.
This is the excerpt from wikipedia where I am confused:
A: "Things that are equal to the same are equal to each other" B: "The two sides of this triangle are things that are equal to the same" Therefore, Z: "The two sides of this triangle are equal to each other"
The Tortoise then asks Achilles whether a second kind of reader might exist, who accepts that A and B are true, but who does not yet accept the principle that if A and B are both true, then Z must be true.
If A and B are true, I think it follows logically that Z is true, and there are no more steps in between where one might disagree. Could someone please point out what i'm not able to follow?
Z must be true if A and B both are held true.