The idea of a "reasonable man" seems like a slippery slope. Who decides what a reasonable man is? Like you said most people are incapable of remaining rational. If that is the case then wouldn't society deem the "reasonable man" to be something like the societal mean.......which would be an irrational person?
Discussion
What's worse, is that there is no definition of reasonable, even though many "laws" hinge on the concept.
I am not talking about laws (legislation), but about law of the common (or natural law).
Common Law: Develops from judicial decisions and precedents, emphasizing consistency through past rulings (stare decisis).
Natural Law: Based on universal moral principles inherent in human nature, discovered through reason, not created by humans.
Legislation: Laws enacted by legislative bodies, codified in statutes, reflecting governmental will and societal needs.
The standard originated in 1837 with Vaughn v. Menlove, establishing that reasonableness is objective rather than subjective.
Courts apply this by asking how a reasonable person would have behaved in similar circumstances to the defendant.
Typically this is a jury question and is augmented by the kind of person, would a reasonable surgeon have done x, y, z. In other words the actual standard of care is context dependent. Also if I was sued for something I wasn’t or shouldn’t be liable I probably would waive my right to a jury—-speaking for myself.