Some people have been promoting a new herbal mixture as a remedy for the common cold  The mixture contains, among other things, extracts of the plants purple coneflower and goldenseal  A cold sufferer, skeptical of the claim that the mixture is an effective cold remedy, argued, Suppose that the mixture were an effective cold remedy  Since most people with colds wish to recover quickly, it follows that almost everybody with a cold would be using it
Ttherefore, since there are many people who have colds but do not use the mixture, it is obviously not effective
The mixture does not have side effects severe enough to make many people who have colds avoid using it.