To be plausible, the necessity constraint must be limited to comparing alternatives that are genuinely available to the defender. Even if an expertly-delivered karate chop could harmlessly render Villain unconscious, this does not make harming Villain unnecessary if Victim is not an expert in karate, even if it is, in some sense, physically possible for Victim to deliver such a blow. It also seems plausible that “availability” should be understood in terms of the defender’s evidence. A hidden trapdoor might offer Victim a means of escaping Attacker without using defensive force. But if Victim has no evidence of this trapdoor, the presence of this less harmful means cannot render force unnecessary (for discussion, see Steinhoff 2019: 174–181).