If you have to decide what to do and you want to do the right thing, the best way is to acquire all the relevant information, to make sure that you do not have any false beliefs that might distort your judgment, and then make your decisions. Of course, that's easier said than done, particularly when we are prone to self-deception. To some extent, we can compensate for our own weaknesses and limitations by seeking the opinions of disinterested and knowledgeable people. Naturally, it is necessary to provide them with as complete, unbiased, and uncontaminated an account as possible. Success is not certain even then but the probability of success is higher.
People disagree about morality. There are lots of reasons for this. We are ignorant. We make mistakes. We rationalize our actions to protect our egos. We are motivated to conform with groups to which we belong. Groups can ignore and dismiss outside critics. And if we get morality wrong as a group, we will still co-operate with each other, so there will often be no cost. Our foundational attitudes themselves do not prevent the development of erroneous moral codes in the short run, So, we should expect variation in moral opinions. We should also expect false opinions that were prevalent at one time to die out with those who held them and new opinions to replace them. We can expect reform when different groups interact and form a larger co-operative group. A form of regression to the mean can occur and the new moral code can more accurately reflect the moral facts. The way to make moral progress as a society is to learn more, to eliminate false beliefs, and to institutionalize impartial decision procedures to deal with conflicts and disagreements.
If evolutionary intuitionism is true, the advice on this page is the best practical advice I can give anyone. There is no need
to study moral theories. In fact, doing so is likely to do more harm than good when it comes to practical decisions. The same goes for my theory. The only reason a practical person should read my book is to understand why I give the advice that I do. I do discuss normative implications but mainly to test the theory: if the results were too far out, we would have reason to reject the theory.