Kant's moral argument can be summarised in 4 points. Point 1, a good will or a person with right moral intentions seeks to bring about the summum bonum. If we take our ethics seriously we can see that we want to achieve the summum bonum. Kant, however was adamant that people should not act nice to receive an award at the end of the act. Kant was convinced that an act is only morally good if it is done for its on sake and without any selfish thoughts. He believed that people should do the right thing because it is the right thing and not for any reward or praise.
Point 2, Kant argued that "ought implies can" - we know that we ought to aim for summum bonum, this means it must be achievable. Kant said that it is "a necessity connected with duty as a requisite to presuppose the possibility of the highest good." This means because we are required by our duty to do good trying to achieve the highest good. Therefore the summum bonum must be achievable for it is a possibility.
Point 3, although the idea of the highest good is a possibility, it is not within our power as humans to reach the highest good. This is because although we strive to reach virtue in our thoughts and conduct, we cannot be sure that happiness is added to virtue. We cannot, on our own, ensure we will get what we deserve from our efforts for we are not omnipotent.
Point 4, Therefore seeing saw we cannot there must be a rational moral being who has the power to bring moral worth and happiness together.
Some people have criticised Kants reasoning. John Hick argues that Kant moved from the idea of logical possibility to the assumption of actuality. Even if it is logically possible it does not follow that it ever actually will happen. Hick also argues that there is a contradiction in Kants argument for Kant says that people are obliged to achieve summum bonum but then says that they cannot reach it for it is impossible for they cannot bring