If A is standing in a vestibule and B threatens him with a razor, can A use force?

In this scenario, A is facing a threat from B who is wielding a razor. The legal principle of self-defense applies when an individual perceives an imminent threat to their safety. Given that B is threatening A with a dangerous weapon, A can reasonably believe that he is in immediate danger. This perception allows A to use reasonable force in response to that threat to protect himself.

The justification for A's ability to use force hinges on the concept of imminent danger and the right to defend oneself against such threats. In the case of authorized object, a person may take necessary steps to safeguard their person when confronted with a direct or immediate threat to bodily harm. Since B's threat with a razor encompasses the necessary elements of a threat that constitutes such imminent danger, A is legally justified in using force.

While alternatives like retreating or escaping could be considered, they don't negate the immediate right to defend oneself when faced with a direct and violent threat like a razor. Therefore, the reasoning concludes that A's best course of action is to use force against B to defend himself.