&gt; It&#x27;s a reasonable seeming law, yes, just as the categorical imperative is - but what if your culture says that the more skulls you collect, the better a person you are? It&#x27;s easy to define a law in isolation from social pressures which defy that law. Take the inquisition - by burning hereticks you saved their souls, and this was therefore good - so do as you would be done by applies, even if it comprises an auto da fé.<p>I think the point is this--if the skull collector became the source of a skull, or the burner became a heretic, they would probably stop thinking those were &quot;good&quot; practices (due to the suffering and death and such), so those acts wouldn&#x27;t satisfy the &quot;do as you would be done by&quot; rule.  Even when those deemed heretics were part of the culture at the time, it&#x27;s doubtful they thought &quot;oh well, I guess this is the right thing to do&quot;.