A fortiori

Now starting and stopping cannot themselves have starts or stops, or, a fortiori, middles either.

We're bound to accept an a fortiori claim because of our prior acceptance of a weaker application of the same reasoning. Frank can't run to the store in less than five minutes, and the restaurant is several blocks further away than the store. Thus, a fortiori, Frank can't run to the restaurant in less than five minutes.