<i>Isn&#x27;t taking all reasonable steps to ascertain consent what the affirmative consent thing is all about?</i><p>Yes.  But if you take those steps and still end up being mistaken -- to take a deliberately bizarre hypothetical, suppose you&#x27;re in bed with someone who has a brain tumour causing them to say &quot;yes&quot; when they mean &quot;no&quot; -- then you might <i>believe</i> that you have that consent when the &quot;experience of the victim&quot; is that they did not consent.