17.        This ad recommends non-prescription¹ Acid-Ease over non-prescription Pepticaid
for relief of excess stomach acid. The only reason offered is that doctors have written 76
million more prescriptions² for the full-strength prescription form of Acid-Ease than for
full-strength Pepticaid. While this reason is relevant, and provides some grounds for
preferring Acid-Ease over Pepticaid, it is insufficient³ as it stands because it depends on
three unwarranted assumptions.
      The first assumption is that the prescription form of Acid-Ease is more popular
among doctors. But this might not be the case, even though doctors have written 76
million more prescriptions for Acid-Ease. Acid-Ease may have been available for
several more years than Pepticaid; and in the years when both products were available,
Pepticaid might have actually been prescribed more often than Acid-Ease.
      The second assumption is that doctors prefer the prescription form of Acid-Ease
for the reason that it is in fact more effective at relieving excess stomach acid. However,
doctors may have preferred Acid-Ease for reasons other than its effectiveness. Perhaps
Acid-Ease is produced by a larger, more familiar drug company or by one that
distributes more free samples. For that matter, the medical community may have simply
been mistaken in thinking that Acid-Ease was more effective. In short, the number of
prescriptions by itself is not conclusive⁴ as to whether one product is actually better than
another.
      The third assumption is that the milder non-prescription forms of Acid-Ease and
Pepticaid will be analogous⁵ to the full-strength prescription forms of each. But this
might not be the case. Suppose for the moment that the greater effectiveness of
prescription Acid-Ease has been established; even so, the non-prescription form might
not measure up to non-prescription Pepticaid. This fact must be established
independently.
      In conclusion, this ad does not provide enough support for its recommending non-
prescription Acid-Ease over non-prescription Pepticaid. To strengthen its argument, the
promoter of Acid-Ease would have to show that (1) the comparison between the number
of prescriptions is based on the same time period; (2) its effectiveness is the main reason
more doctors have prescribed it, and (3) the comparative effectiveness of the two non-
prescription forms is analogous to that of the prescription forms

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