etc/proofgeneral-settings.el

remove "safe" (as suggested by Tobias) and added "arith" to "try"

;;; Options for Proof General

;; Examples for sensible settings:

(custom-set-variables '(indent-tabs-mode nil))

;(custom-set-variables '(isar-eta-contract nil))

;(custom-set-faces
; '(proof-locked-face
;   ((((type x) (class color) (background light)) (:background "lightsteelblue2")))))