Is it ever possible to know what to do? For example, when it comes to eating, should you eat the way I eat or recommend eating? Should you eat the way anyone else eats or recommends eating?
Instead of following someone else, become your own authority. Why? There are no authorities about what to do.
There is no knowledge of right and wrong. I follow the usual convention and use ‘right’ and ‘wrong’ to refer to actions done by moral agents. Actions have causes, features, and consequences. A cause of an action might be your motivation to eliminate your sensation of being hungry. A feature of an action might be your intention. A consequence of your action might be the annihilation of your hunger.
As I have argued in these posts, the idea of knowledge goes with the idea of demonstrative evidence, whereas the idea of opinion goes with the idea of nondemonstrative evidence.
Is it possible to have knowledge or demonstrative evidence about what to do? Is it possible to have knowledge or demonstrative evidence about right and wrong?
No. Here’s why. It’s senseless to claim that a right act has bad consequences or that a wrong act has good consequences. The consequences of an act are inseparable from its moral evaluation.
There is no knowledge of the future. Nobody has demonstrative evidence about what will happen. Mistakes in thinking about what will occur are always possible.
The consequences of an act are in the future. Since knowing them is necessary to knowing whether or not an act is right or wrong and since it is impossible to know them, it is impossible to know that an act is right or wrong.
Like me, you’d like to know how to eat well. You’d like to know how to eat now so that your future is as good as possible. You are never in an epistemic position to know what the future will be. Since knowing how to eat well depends upon that impossibility, you cannot know how to eat well. Furthermore, nobody else can know that either. This is why there are no authorities about what to do.
Do not, then, think that I know what you should eat. I don’t. Nobody else does either. Do not, then, think that I know what you should do. I don’t. Nobody else does either.
Judgments about right and wrong are opinions. There’s no such thing as knowledge about and wrong.