Kant explains why actions for the sake of duty and only duty are the only actions with moral worth in this section. He starts by asserting that the only quality with inherent goodness is a good will. This is true because all other qualities can be used for evil without a good will. Because this is true, we should only decide what action has moral worth based on whether or not a good will was used. The way to observe this is to observe whether or not an action was from duty and not from inclination. This is true because satisfying inclinations does not require a good will. Following from these assertions, an action has moral worth only if it is from duty (italicized to imply a specific meaning). It is unclear exactly what is meant by “moral worth” but anything with moral worth is a right action. Kant also says that something is a duty to someone if and only if they think that it should be a universal duty.
The problem I see with this theory is that it is impossible to follow for someone who is trying to follow it. If I adopted this philosophy upon reading Kant and understanding it, I would be inclined to follow my duties because I want to do things with moral worth. Further, I want my actions to have moral worth because I want to be a good person. Although I would be consistently conforming with duty I would be acting from self interest and therefore giving my actions no moral content. Kant says that actions with this motivation “however it may conform to duty and however amiable it may be, has nevertheless no true moral worth but is on the same footing with other inclinations” – Kant (11). He says this when discussing a soul with an inner satisfaction in spreading joy. This means that compliance with duty and good intentions are not sufficient to attain moral worth, which I disagree with. Kant gives a few examples of people acting from duty but does not fully explain how people can consistently do it. A common theme among actions with moral worth is some resistance to inclination, although I do not think this is necessary.
I would change The necessity of acting from duty to only acting with duty. This means that to have moral worth an action must comply with duty and be motivated in some way by duty. This means that any action complying with duty does have moral worth as long as the agent, or person completing the action, has any motivation stemming from this duty. A mere acknowledgement of an action as a duty would suffice as motivation. A person who is inclined to spread joy could act on that inclination with moral worth if they also understand that it is a duty. If the agent acts solely on their inclination the act is not with duty at all and thus has no moral worth.
This philosophy does well levelling the playing field between naturally malicious and beneficent people. All that matters to Kant is a person’s volition. Someone lucky enough to be born with beneficent inclinations is not necessarily better than the unfortunate soul born malicious who must exercise their volition frequently. Each person is held accountable to find and use their good will.