 McTaggart also argues that the A series is inherently contradictory. For, he says, the different A properties are incompatible with one another. No time can be both future and past, for example. Nevertheless, he insists, each time in the A series must possess all of the different A properties, since a time that is future will be present and then will be past. McTaggart concludes that, since neither the A-series nor the B-series can order the time series, time is unreal.