A firm's leaflet reads: 'Our water purifier is endorsed by Dr Menon, whose work on heart disease is known throughout the country. It is therefore established that the purifier takes the fluoride out of this district's water.' The leaflet's reasoning is most open to criticism because it

Whether a cartridge strips fluoride out of water is settled by testing the water before and after, and eminence in heart disease gives no special access to that answer. The leaflet borrows the weight of a name earned elsewhere. The price of the purifier is not what the claim is about; the claim does not require that every household's water contain fluoride, only that the purifier remove what is there; and how widely the name is known would matter to the leaflet's persuasiveness, not to the truth of what it asserts.