All imperatives command either hypothetically or categorically. Hypothetically require a practical necessity of an action as a means to achieve happiness or the primary end. Categorically is the action as needed of itself, without a secondary end as a means to the primary end. The one end that all rational beings are know to have with respect to the application of imperatives is happiness. From this Kant argues that there is but one categorical imperative, being: "Act only on that maxim whereby thou canst at the same time will that it should become a universal law.".
Examples presented by Kant to back his argument state that, universal law of nature cannot contradict itself. In General we do not in fact will that our maxims should be a universal law, since its impossible, yet we will the opposite should stay a universal law, only we assume the liberty to make exceptions of our own maxims for our own benefit. Therefore, certain principles should be objectively necessary as a universal law, yet subjectively should not be universal; however there are our exceptions like something that is an end in itself. .
Kant's foundation of this principle is that rational nature exists as an end in itself, almost god like. Since man views his being as an end in itself, this is a subjective principle of human actions, however at the same time an objective principle since all see it in this same way. Suicide for example, there is a necessary duty to oneself, but does not work since the actions are not consistent with the ideal of humanity as an end in itself, committing suicide would be to use a person merely as a means. Yet man cannot be used merely as a means, but must in all actions be considered as an end in him. .
Kant also argues that it is not enough that the action does not violate humanity in our own person as an end in itself, but also it must harmonize with it. According to Kant mans natural end is his own happiness, and no one should contribute anything to the happiness of others, as long as that person did not intentionally withdraw anything from it, after all this it would but only harmonize negatively not positively with humanity as an end in itself.
