Nothing of the sort is implied. Everyone can have their own should (or not, as the case may be). But if you know you should do something, presumably you're past such useless philosophising. I know I should be nicer to the people I love, and

> Why is there a "should"? Is there a unique and universal way to determine what someone should do? Given the same situation two different people can act in two different ways. Is there a rule implying that one is right and the other is wrong?

strikes me as a rather obtuse response to that.

> Is there a rule implying that one is right and the other is wrong?

most of the time, yes!

We are not living in a void, we live in societies, complex societies. with lots of rules, dos and donts, should and shouldn't.

By this I mean acting according to your own judgement. It's not an objective should, but a subjective one.

Moral incontinence is a problem most people will struggle a lot more with than convoluted scenarios involving trolleys.