--- a/src/HOL/Isar_Examples/Higher_Order_Logic.thy Mon Nov 07 21:40:43 2016 +0100
+++ b/src/HOL/Isar_Examples/Higher_Order_Logic.thy Mon Nov 07 21:52:41 2016 +0100
@@ -300,7 +300,7 @@
theorem (in classical) Peirce's_Law: "((A \<longrightarrow> B) \<longrightarrow> A) \<longrightarrow> A"
proof
- assume a: "(A \<longrightarrow> B) \<longrightarrow> A"
+ assume *: "(A \<longrightarrow> B) \<longrightarrow> A"
show A
proof (rule classical)
assume "\<not> A"
@@ -309,7 +309,7 @@
assume A
with \<open>\<not> A\<close> show B by (rule contradiction)
qed
- with a show A ..
+ with * show A ..
qed
qed