Definitions
from Wiktionary, Creative Commons Attribution/ShareAlike License
 adj. Having two conditions
 n. An "if and only if" conditional wherein the truth of each term depends on the truth of the other
Etymologies
Examples

In logic the word Iff means 'if and only if' – the biconditional.

But desirebased reasons theorists, as such, are committed, as internalists, as such, are not, to accepting a specific understanding of this internalist biconditional that reads the order of determination from right to left: what speaks to my desires determines what reasons I have and not vice versa.

Another way of expressing this is by saying that 2P7 is not a biconditional.

Another response consists in removing the biconditional in (ME1), replacing it with a weaker principle

Since the following biconditional is also a straightforward consequence of the axioms:

Setting these questions aside, we can note that the (EC) biconditional has been used in two different ways: as a way of characterizing assertoric correctness in terms of truth and evidence, or as a way of characterizing truth in terms of correctness and evidence.

However, the relations corresponding to such predicates are strictly weaker than PP and PE and no biconditional is provable in M that would yield a corresponding definiens of

Concerning the first sort of worry, one could of course construe every restricted formulation as a biconditional expressing both a sufficient and necessary condition for the existence of an upper bound, or a sum, of a given pair or set of entities.

We therefore need a principle that restricts the quantification in the right half of the biconditional to possible worlds; how to do that without appealing to modal notions is an unsolved problem.

Someone who believes that being a male sibling is necessary and sufficient for being a brother will not be led to doubt that biconditional by the existence of an intersex person who is on the border between being male and being female.
Comments
Log in or sign up to get involved in the conversation. It's quick and easy.