Final answer:
According to Kantian ethics, a morally good act is determined by its nature, the agent's intention, adherence to duty, and universal applicability as expressed by the Categorical Imperative. It emphasizes the importance of duty and rationality over the outcomes of an action.
Step-by-step explanation:
The factors that determine whether an act is considered morally good according to Kantian ethics are rooted in the nature of the act, the intention of the agent, and the principles of universality and duty. Kant posited that a morally good act must be undertaken out of a sense of duty, and this duty is determined by whether the action's guiding maxim can be universally applicable to others. He introduced the concept of the Categorical Imperative, which demands that one only acts according to a maxim that could be adopted universally. This implies that the nature and the intention behind an act are primordial, and the agent’s intention must be to act out of duty, beyond personal desires or outcomes. According to Kant, intentions and the accordance of actions with duty and rational thought properties give an act its moral worth, irrespective of the outcomes that may follow.