<i>Basing his opinions on blogs and a particular internet community. Rather than acquiring an understanding from the scientific source material on these issues.</i><p>I expect that approximately 100% of the people who argue for vaccinating children are doing <i>exactly</i> the same thing. The number of parents personally familiar with the scientific evidence and qualified to make an independent judgement is probably tiny.<p>This then leads to the argument that non-experts should respect the scientific consensus, but then how does a non-expert evaluate the credentials of a commentator to determine whether they are in fact an expert and part of a real scientific consensus? Bad science abounds in the media, and there is a lot of money to be made from peddling it, and some of the people presenting it are very convincing because that&#x27;s what they do.<p>This is a fundamental problem with any debate about policy based on scientific merit: at some stage, there is always a degree of trust involved for anyone who is not personally an expert in the subject matter, which in practice means almost everyone. This opens a gap for the critics and sceptics. And crucially, <i>this is a legitimate concern</i>. There <i>is</i> room for the &quot;science&quot; to be wrong, and <i>sometimes it has been</i>.<p>The rational point is that it is far more likely that a consensus among large numbers of people who are probably scientific experts will be correct. When that is the best information we have to go on, as it nearly always will be, we should probably make our decisions consistent with that consensus rather than in opposition to it to give ourselves the maximum chance of a positive outcome.