The argument in the first example is just wrong. 1) His value might be that it looks like there is a security guard on duty, and that a) encourages customers, b

The argument in the first example is just wrong. 1) His value might be that it looks like there is a security guard on duty, and that a) encourages customers, b) discourages robbers. A rock cannot do that. 2) He could do that, but he probably won't, because it's boring to just sit there. Once in a while, he will walk around, looking, paying at least a little attention. It makes robbery riskier.