In the later version of the argument, in "The Nature of Existence", McTaggart no longer advances the circularity objection. This is, arguably, because by then he has come to treat tense as a simple and indefinable notion, and thus cannot contend that the terms need to be explained at all in order to be applied. He now instead argues that even if it is admitted that they are simple and indefinable, and thus can be applied without further analysis, they still lead to contradiction.