I would like to know if duty implies value. If I have the duty to take care of my daughter, does that imply that it is better that I take care of her than that I don't? If two people promise each other to meet that evening, is it then better (at least, according to their promises) that they meet? If I have the duty to join my country's army, is it better that I do than that I don't? Thank you.

Great questions. Many philosophers recognize that we have multiple duties which sometimes conflict. And they also recognize different degrees of complexity that come with duties. So, in a parent-daughter relationship, it is widely acknowledged that a parent does have a duty to take care of her and thus, it is recognized that, other things being equal, it is better to care for her than not but some of the following circumstances can come into play: imagine that there are great social and political forces that would make it fatal if the parent comes forward to acknowledge that he or she is the parent. Or imagine that the parent was abusive and for example a daughter is utterly estranged from a father she never wishes to see again. And sometimes duties such as those you mention can present us with cases when one duty might be served by following another duty. So, your duty to care for your daughter might be satisfied by your joining an army: imagine that your city is under aggressive military attack and the best way to take care of your daughter or the best way you can contribute to her survival and safety is to join in the military defense of your city.

I hope you will not think this reply is too frustrating but, in many cases of assessing duties philosophers add an "all things considered" condition. So, you are right in thinking that if we have a duty to keep promises, then keeping them is better than not keeping them. This would be true or it is true in most, ordinary conditions. But that is not what most philosophers think when it comes to promises that are made to carry out unjust acts. `Making vows or oaths or promises can be binding, but when these are undertaken to carry out wicked acts, most philosophers have held they are not binding. In fact, making a vow or oath or promise to do something unjust may well make the action even worse. I suggest that if you wrong me by stealing my money, your act is wrong, but it would be less of a grave wrong if the act was thoughtless and impulsive, versus the same amount of money was taken but you did so to fulfill a vow or oath or a promise you made, let us imagine, to members of your gang that you would commit the robbery. I believe the latter would be more of a grave wrong as it would stem from a considered, deliberate, intentional act whereas the thoughtless wrong might indicate weakness of will but not reflect a deep matter of character and commitment. The inability of our duty to keep promises to trump our ordinary duties comes out in considering the first case you mention in your question. Imagine a parent in a state of emotional confusion and despair promises not to take care of her child. When the parent recovers her sane state of mind, imagine she reasons: I now see that I do have a duty to care for my child, but because I promised not to, I have a duty to ignore my duties as a parent.

One of the great philosophers who sought to rank our duties in the 20th century was W.D. Ross. You can track some of his work through the Stanford Encyclopedia of Philosophy.

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