A instigates B, a person of unsound mind, to set fire to a dwelling house. B, incapable of knowing the nature of the act that he is doing what is wrong or contrary to law sets fire to the house in consequence of A's instigation.
Which one of the following statements legally correct?

A instigates B, a person of unsound mind, to set fire to a dwelling house. B, incapable of knowing the nature of the act that he is doing what is wrong or contrary to law sets fire to the house in consequence of A's instigation.
Which one of the following statements legally correct? Correct Answer B has committed no offence but A is guilty of abetting the offence

Related Questions

Principle: Nothing is an offence which is done by a person who, at the time of doing it, is, by reason of intoxication, incapable of knowing the nature of the act, or that he is doing what is either wrong, or contrary to law, provided that the thing which intoxicated him was administered to him without his knowledge or against his will.
Factual Situation: Ram, Shyam and Vipin were friends. Vipin was in love with Anita and wanted to marry her. One day she told him that her marriage was fixed with a rich NRI and that he should not disturb her again in future. Vipin, who became depressed, told this to his friends. Ram suggested that they should go to a nearby bar and drink some Beer so that Vipin could relax. As Vipin was not habituated to drinks, initially he declined but later at the bar Ram told Vipin to take a little Whisky, which he did hesitatingly, After a while Vipin became totally intoxicated and started to say that Anita ditched him. Shyam, who was also drunk then said. " If you are so worried, go and kill her". A little while later all three friends parted company. Vipin went straight to Anita's hostel, called her out and shot her.
B, a man of unsound mind, sets fire to a dwelling house on A's instigation. Here, B is exempted from criminal liability (Section 84, Indian Penal Code), but A is guilty of abetting mischief by fire with intent to destroy the house. The principle for this criminal liability may be explained by which one of the following explanations?
Assertion (A): Nothing is an offence which is done by a person who at the time of doing it by reason of unsoundness of mind, is incapable of knowing the nature of the act.
Reason (R): Mistake of fact is a good defence and Mistake of Law is no defence.