The defendant was liable because the reasonable person does not set themselves alight. 

The defendant was not liable because his actions were involuntary and therefore not negligent. 

The defendant was liable because he directly caused physical harm to the claimant by his positive act. 

The defendant was not liable because he owed no duty of care while acting under a delusion. 

The defendant was not liable because the harm was caused by the claimant's own intervention.