“The government feels their convulsions might have happened anyway. Dr. Murphy disagrees …”

<jats:title>Abstract</jats:title> <jats:p>During the 1970s and 1980s in the UK and USA, there were concerns about the safety of the diphtheria, tetanus, and pertussis vaccine, with some scientists arguing against it. Similarly, in the 1980s and 1990s, there were dissenting views on the widely accepted idea that HIV causes AIDS. These debates raise the question of what lay people should do when experts disagree. There are two approaches to this issue. First, one can try to identify who among the scientists is a true expert on the topic. If this is unclear, the best approach is to look for the consensus view, usually held by most experts in the field and often expressed by professional associations and organizations. Listening to the majority is not about democracy but about recognizing the outcomes of critical interrogation within a scientific field.</jats:p>