If we have evidence that a subclass of our moral beliefs is not subject to these undercutting defeaters, then that evidence defeats the defeater, and justification is restored.
"Whatever initially made $B$ justified continues to justify $B$ once the defeater has been defeated.
An argument is self-defeating if it supports a defeater for one of its own defeasible steps.
Call the result of deleting B from S's evidence base 'EBS reduced with respect to B'EBS−BBS−B' for short.[11] And now the suggestion — call it 'the reduction test for defeat' — is that A is a defeater for B just if B is appropriately improbable with respect to the conjunction of A with EBS−B.
(2013, 413) Sinnott-Armstrong would say that in order for the undercutting defeater (the 1st stranger's comment) to be defeated by the factory worker's claim that the stranger is a trickster, the factory worker's comment must provide McCoy with a reason to think that his belief was formed reliably.
Obviously that can't be right; if it were, every putative defeater could be turned aside in this way and defeat would be impossible.
A relation of defeasible consequence clearly must be nonmonotonic, since a defeasible inference can be defeated by adding additional information that constitutes a rebutting or undercutting defeater.
But defeat is not impossible; it sometimes happens that one does acquire a defeater for a belief B, by learning that B is improbable with respect to some proper subset of one's evidence base.
If that were sufficient for A's not being a defeater of B, however, no member of the evidence base could ever be defeated by a new discovery; and that can't be right.
The most prominent of these was a musalsal on the life of Sultan Saladin, the 12th-century defeater of the Crusaders and liberator of Jerusalem.
Popiełuszko, a political dissident murdered by the communist regime, and the Black Madonna of Czestochowa, mutilated by a Hussite heretic and later the miraculous defeater of invading Swedes, both carry strong messages about heroic Polish resistance to foreign foes and the threats posed to Catholics by unbelievers.
