--- a/Geometric.st	Fri Feb 10 11:19:54 2017 +0100
+++ b/Geometric.st	Fri Feb 10 11:20:44 2017 +0100
@@ -330,6 +330,16 @@
     "Modified: 12.2.1997 / 12:10:12 / cg"
 ! !
 
+!Geometric class methodsFor:'queries'!
+
+isAbstract
+    "Return if this class is an abstract class.
+     True is returned here for myself only; false for subclasses.
+     Abstract subclasses must redefine this again."
+
+    ^ self == Geometric.
+! !
+
 !Geometric methodsFor:'converting'!
 
 asFiller