Oh, excuse me. I was not aware this was still the eighteenth century. Where's my powdered wig?
The problem is, "reason" is 100% amoral. It can be used for any purpose, moral or immoral. A mass murderer can use "reason" every bit as well as you do, sir (or madam).
The only "natural laws" are those that say things like "if you jump off a cliff you will fall." There is no "natural law" promoting morality or ethics.
I don’t accept your premises. What does the eitheenth century have to do with anything? You say that there are no natural laws promoting moral values or ethics. There is, The law of identity. Your argument is that reason is impudent in questions of values. I disagree.