diff --git a/joy/library.py b/joy/library.py
index eb911bb..e6920af 100644
--- a/joy/library.py
+++ b/joy/library.py
@@ -908,7 +908,6 @@ S_pop = Symbol('pop')
 S_step = Symbol('step')
 S_times = Symbol('times')
 S_swaack = Symbol('swaack')
-S_truthy = Symbol('truthy')
 
 
 @inscribe
diff --git a/thun/defs.txt b/thun/defs.txt
index c2c4a5c..741ba8a 100644
--- a/thun/defs.txt
+++ b/thun/defs.txt
@@ -1,5 +1,6 @@
 -- == 1 -
 ++ == 1 +
+?  == dup bool
 anamorphism == [pop []] swap [dip swons] genrec
 app1 == grba infrst
 app2 == [grba swap grba swap] dip [infrst] cons ii