This article focuses on the moral development ideal of William Whewell, one of the most important intellectual figures of the 19th century Britain. According to Whewell, morality is an ideal of development. This is a process that continues throughout human life in which there is true happiness at the end. In every moment we live, we have the opportunity to be a more virtuous and better person. According to him, the most important task of human beings is to realize this ideal of development. The motivation behind this ideal is to bring morality, science and religion together in a rational system in harmony with each other. The source of this motivation is the criticism of irrationality and inconsistency directed by utilitarian thinkers (especially, John Stuart Mill), the most important opponents of ethical intuitionism. As a way of making these three areas consistent with each other, Whewell bases morality and science on a theological basis. Accordingly, God, the creator of the universe and human beings, has laid down certain principles that will regulate both nature and human actions. The duty of morality and science is to discover these principles. Therefore, morality and science are simply a process of discovery. Whewell argues that the basic principles of morality can only be known intuitively. The main reason why Whewell is considered within the ethical intuitionist tradition is this view. But this process of knowing the basic principles does not in any way imply an irrationality. The basic power that intuitively perceives these principles is reason. Conscience is a faculty that approves the judgments of reason. However, in Whewell’s philosophy, conscience corresponds to an aspect of reason rather than being a faculty separate from reason. Thus, Whewell is distinguished from the intuitive moral thinkers who regard conscience as a faculty separate from reason, which grasps the basic principles of morality. According to Whewell, conscience is the guide of a human being but the judgments of conscience can sometimes be mistaken. Therefore, conscience must be constantly controlled and developed by reason. This point is where Whewell bases his moral philosophy. Because one’s duty is to continuously improve their conscience and make all their judgments in accordance with the highest rule. This corresponds to moral development. The concepts of the highest good, duty, and virtue are extremely important in moral development. The ultimate rule in Whewell’s philosophy expresses the will of God. The obligation to obey God’s commands corresponds to duty, and fulfilling the duty corresponds to virtue. Thus, any violation of duty is a violation of God’s command. Failing to do the duty is to go against the will of God. In a religious context, this corresponds to sin. Whewell argues, however, that the ideal of moral progress cannot be fulfilled by reason alone. The main reason for this is the limited structure of reason. Therefore, reason needs the help of revelation in this process. Nevertheless, in order to preserve the rational ground of his moral philosophy Whewell prioritizes reason over revelation and natural religion over revealed religion. However, Whewell still argues the help of revelation necessary for the fulfillment of the ideal of progress. He even says that those who do not accept this help of revelation and do not believe in revelation should be condemned. Because, according to him, this ideal of development can be completed with the information beyond the reach of reason that can only be bestowed by revelation. Whewell goes so far as to argue that no one was able to complete their moral evolution before Jesus Christ descended on earth. He also shows that revelation did not occur at that time as a justification. The question of whether Whewell’s claim has an impact on the rationality of his philosophy is the main problem of this article. Here I argue that Whewell’s approach that the ideal of moral development cannot be completed without the help of revelation makes his philosophy controversial, even if it does not completely remove the rational ground of moral theory