Kantianism is based on Kant’s categorical imperative. For Kantians, there are two questions that we must ask ourselves whenever we decide to act:  (i) Can I rationally will that everyone act as I propose to act?  If the answer is no, then we must not perform the action.  (ii)  Does my action respect the goals of human beings rather than merely using them for my own purposes?  Again, if the answer is no, then we must not perform the action. Kant’s theory is an example of a deontological moral theory which supposes that the rightness or wrongness of actions does not depend on their consequences but on whether they fulfill our duty (Rosen et al., 2015). On the other hand, the principle of utilitarianism suggests that actions are moral when they lead to happiness but wrong if they cause pain or prevent pleasure (Rosen et al., 2015). This paper argues that Kantianism should guide our moral actions since it respects humanity. On the contrary, utilitarianism should not be used since it allows immoral actions for the sake of achieving the greater good.
To start with Kantianism is universal. In other words, it bases morality of actions by considering whether that action is acceptable to all humans. Kant argues that a person is good or bad depending on the motivation of their actions and not on the goodness of the consequences of those actions.  By “motivation” I mean what caused you to do the action (i.e., your reason for doing it).  Kant argues that one can have moral worth (i.e., be a good person) only if one is motivated by morality.  In other words, if a person’s emotions or desires cause them to do something, then that action cannot give them moral worth (Rosen et al., 2015).  This may sound odd, but there is good reason to agree with Kant.
Kantianism and utilitarianism have different ways for determining whether an act we do is right or wrong. According to Kant, we should look at our maxims, or intentions, of the particular action. Kantians believe human life is valuable because humans are the bearers of rational life (Rosen et al., 2015). In other words, humans are free rational beings capable of rational behavior and should not be used purely for the enjoyment or happiness of another.  On the other hand, Utilitarians believe that we should do actions that produce the greatest amount of happiness (Rosen et al., 2015). The problem with this, however, is that it could involve using people as mere means and may lead to the sacrifice of lives for the greater good.
Utiliarians justify punishing an innocent party if it is necessary to bring about a sufficiently important good. Additionally, promises, which are typically binding in our society, can be broken if it produces a greater good (Rosen et al., 2015). This can be applied to any promise, including those made with loved ones. Utilitarianism sometimes involves the sacrifice of an individual’s happiness or life in order to promote the greatest amount of happiness and the least amount of misery.
What is more, Kantianism does not forbid happiness. One might think Kant is claiming that if one of my intentions is to make myself happy, that my action is not worthy.  This is a mistake.  The consequence of making myself happy is a good consequence, even according to Kant.  Kant clearly thinks that people being happy is a good thing.  There is nothing wrong with doing something with an intended consequence of making yourself happy, that is not selfishness.  You can get moral worth doing things that you enjoy, but the reason you are doing them cannot be that you enjoy them, the reason must be that they are required by duty.  Also, there is a tendency to think that Kant says it is always wrong to do something that just causes your own happiness, like buying an ice cream cone.  This is not the case.  Kant thinks that you ought to do things to make yourself happy as long as you make sure that they are not immoral and that you would refrain from doing them if they were immoral (Rosen et al., 2015).
It is easier to determine an action as morally right in Kantian ethics than in utilitarian ethics. When data is scarce, Kantian theory offers more precision than utilitarianism because one can generally determine if somebody is being used as a mere means, even if the impact on human happiness is ambiguous. Kantians consider only the proposals for an action that occur to them and check that these proposals use no other as mere means (Rosen et al., 2015). Contrastingly, utilitarianism compares all available acts and sees which has the best effects (Rosen et al., 2015). Although utilitarianism has a larger scope than Kantianism, it is a more timely process. The decision-making method of calculating all of the potential costs and benefits of an action is extremely time consuming and leaves little time for promoting happiness, which is the Utilitarian’s goal.
References
Rosen, G., Byrne, A., C. Joshua., Harman, E., & Shiffrin, S. (2015). Groundwork of the metaphysics of morals: The Norton Introduction to Philosophy. pp. 800-812.
Rosen, G., Byrne, A., C. Joshua., Harman, E., & Shiffrin, S. (2015). Utilitarianism: The Norton Introduction to Philosophy. pp. 790-798.