Jerry LRC, In logic, the statement "p is equivalent to q" is a synonym for "p iff q", which is a synonym for "(if p then q) and (if q then p)". That is the relation that Peirce intended when he said that the scroll is equivalent to a nest of two negations. In mathematics, there is an open-ended variety of equivalence relations. For more information, see my tutorial: http://jfsowa.com/logic/math.htm where I state the following definition: An equivalence relation is reflexive, symmetric, and transitive. The archetype of an equivalence relation is equality: it is reflexive, because x=x; it is symmetric, because x=y implies y=x; and it is transitive, because x=y and y=z imply x=z. As another example, born under the same sign of the zodiac is an equivalence relation over the set of all people. Whenever an equivalence relation is defined over a set, it divides the set into equivalence classes. The zodiac relation divides the set of all human beings into 12 equivalence classes that have the traditional labels Aries, Taurus, ..., Pisces. That tutorial has been downloaded over 200,000 times. You might find it useful. John
_ _ _ _ _ _ _ _ _ _ ► PEIRCE-L subscribers: Click on "Reply List" or "Reply All" to REPLY ON PEIRCE-L to this message. PEIRCE-L posts should go to peirce-L@list.iupui.edu . ► To UNSUBSCRIBE, send a message NOT to PEIRCE-L but to l...@list.iupui.edu with no subject, and with the sole line "UNSubscribe PEIRCE-L" in the BODY of the message. More at http://www.cspeirce.com/peirce-l/peirce-l.htm . ► PEIRCE-L is owned by THE PEIRCE GROUP; moderated by Gary Richmond; and co-managed by him and Ben Udell.
