John Paul points out that although man's technological and material accomplishments certainly stand as authentic signs of man's greatness, they provoke a disquieting question: "Does this progress, which has man for its author and promoter, make human life on earth 'more human' in every aspect of that life? Does it make it more 'worthy of man?'" Yet again, the true measure of good is the effect on the human person, not just mere accomplishment and accumulation. The encyclical teaches that even if contrary to its intention, any purely materialistic system that essentially ignores the human person must in the end condemn man to being a slave of his own production.