Immanuel Kant's conception of nature is one that exists in a realm of absolutely necessary causal laws. According to Kant, time and space are pure intuitions of our faculty of sensibility, and our concepts of physical laws, like causation, are pure intuitions of our faculty of understanding. Our sensory experience is therefore processed by our faculty of sensibility, organizing what appears to us according to our intuitions of time and space. It is in this way that sublime is an experience in which our human freedom encounters it's limitation, as the overwhelming experience of an incomprehensible phenomenon of nature enables us to realize our rational subordination to it. That is to say that our sense of the sublime a part of our faculty of reason. When apprehending a phenomenon of nature, we perceive it as bewildering or even edifying. This puts us in touch with ideas of rationality or what we can comprehend. It is in this way that sublimity resides not in the object of our perception but in reason itself. It is within the faculty of reason itself to identify it's limitations, however, without an experience of this limitation, of the sublime or something like it, we would not be able to identify these limitations.
A parallel experience to that of the sublime is Heidegger's understanding of "being-towards-death." For Heidegger, one's own existential reality is defined by his/her inescapable finitude - everyone dies. Being-towards-death is not a concept that is supposed to bring us closer to physical death itself but rather it is a mode of existence. For Heidegger, death is determined by its inevitability, but an authentic being-towards-death is one that understands the indeterminate nature of one's own inevitable death - as no one knows how, why, when or where they are going to die.
At the very outset of life, there is always the possibility for death. Any projections or possibilities of what could happen in the future are inseparable from the past or present. For Hiedegger, death is not some simple linear physical degradation or a lofty idea of what could happen, but rather, death is contained within one's own life. In this way, Heideggers conception of death is not meant to place death outside of us or at some indeterminate future but rather proposes that a person's death is ever-present in one's self.
Similarly, an experience of the sublime, whether it be a swirling mass of clouds or a vastly large ocean, brings our limitation into appearance. We recognize ourselves as something more than a given set of determinate relations bound by laws of nature. Because of this experience, we are able to recognize ourselves as freedoms existing within physical and rational boundaries. An experience of the sublime is one that is both alienating and engaging at the same time. We begin to recognize ourselves as distinctly separate from the natural phenomenon apprehended. Through this separation we understand that there are some things that are our of our control, yet it is the lack of control that draws us in and sparks our curiosity. Conversely, being-towards death is not founded in experience but rather a lack of experience. One's own death is only experienced by the individual and, according to the nature of death, is inexpressible. There is no possible way that one can reflect upon one's death in the same way that one can reflect upon an experience of the sublime. However, both contain acknowledgments of limitations that are not simply exterior to one's self, but rather, a part of one's being. For Heidegger, death is a necessary consequence of life and can be found within life itself. In the same way, it seems that limitation, and an acknowledgment of that limitation, is a necessary consequence of having a rational faculty at all.
Both Heidegger's being-towards-death and Kant's conception of the sublime indicate a confrontation with one's own finitude, followed by an overcoming of this finitude. Both concepts are described as deeply alienating yet severely engaging. For Heidegger, being-toward-death calls ones individual self out of it's situation in the world, and is edifying insofar as it allows one to re-evaluate one's life from the standpoint of one's own mortality. A feeling of "angst" or anxiety concerning the paradox between freedom and finitude may follow from this realization. However, this angst is not fixated on an object, but instead, one is anxious about one's existence in general - how one should go about living one's life or designing one's self. It is this realization of what is hidden, the truth, as well as the existence of hiddenness itself, the fact that the truth is hidden, that can bring us closer to the truth in general.
In the same way, an experience of the sublime is one's own and no one else's. It is a personal, subjective experience that is difficult to give an account of. One simply must experience the sublime in order to understand it. In this way, Kant's conception of the sublime is similar to Heidegger's "being-towards-death" insofar as they expose the limitations of human freedom and reasoning and contextualize an individual's existence in the world. It is through my acknowledgment that I am a singular individual that that is fated to die just like every other human being that I begin to realize my limitations. Additionally, an awareness of my mortality enables me to see a the world as a larger thing than myself or what I can perceive. The Alps covered in snow standing before me are not just a visually stunning and emotionally provocative phenomenon but a reminder of my own mortality, as the Alps existed before me and will exist after me. The life span of something in nature is completely beyond my intuitive comprehension, and it is in this way that the sublime renders me dumbfounded. The Alps transcends my understanding in the same way that the world outside of myself transcends my mortality.
In both Heidegger's account of death and Kant's account of the sublime, the person who is the subject of the experience must encounter his/her finite existence and find meaning. In the case of the sublime, it is less clear that finding meaning is a result of that experience. Additionally, it is probably not the intention of Kant to point to an existential crisis created in the viewer of a sublime phenomenon. However, both accounts aim to elucidate the limitations of human freedom and therefore human existence. It seems that both Heidegger and Kant agree that not only are there limitations to human freedom, but that these limitations are internal. Perhaps we need outside experience in order to illuminate this tension, but it seems to be completely within the realm of the individual to make of that experience what they will. In both cases, anxiety seems more than likely to occur when encountering the sublime as well as grappling with being-towards-death. Both enable a confrontation with the limitations of human rationality and freedom in a personal and even frightening manner.