Heidegger’s destruktion of Cartesian metaphysics stands as one of his most arguably revolutionary and monumental contributions to philosophical thinking in Being and Time. Not only did Heidegger’s critique of Descarte’s epistemology implicate the latter’s divorce of the subject from the world, but also its implications within which the Cartesian subject as self-enclosed and distinct from its world gave rise to generations of philosophical “pseudo-problems,” most notably the problem of the external world and the problem of other minds.
Accordingly, the very problems taken to be the central focus of modern philosophy (vis-a-vis epistemology) are derived on account of the fact that they have taken-for-granted certain assumptions, beginning with the mis-conception of the human-being as first existing and then finding its world. For Heidegger, human being is being-in-the-world and being-with-others; these are the very structures of human existence itself. The problem of Cartesianism is the problem of the positing of the human being as the ontological center, and thus leads invariably to subjectivism.
For Descrates, doubt pushes knowledge to its outermost limits, and thus is the means by which first principles are determined: whatever can survive Cartesian “methodological doubt” thus serves as the foundational principles of philosophical thinking. Thus, when Descartes applies his thoroughgoing doubt to all, he inevitably comes to the conclusion that he, the doubter, must in fact exist — and this is the unquestionable grounds upon which philosophy in the Cartesian (metaphysical) tradition takes as its starting point. Thus, the very act of doubting inevitably proves that the “I” for whom does the doubting — it follows that the “I” must exist (or at least think).
Thus, Cartesianism makes the move from “I think” to “I exist.” But this doesn’t really seem to accord with the phenomena (and Heidegger goes on to show that this is indeed the case) by which the individual “I” must exist in the first place in order to “think.” It is from here that Cartesian subjectivism mis-construes human being (the “thinking substance” as self-evident grounding.
At the same time, Heidegger’s existential analytic of Dasein’s radical finitude in its authentic being-towards-death does indeed seem to manifest a “destructive retrieval” and creative repetition of Cartesian doubt. But whereas Descarte’s “doubt” was a cognitive method by which all assumptions were put to the wall of doubt in order to see if they could measure up, Heidegger’s thinking as regards Dasein and its mortality. If we look closely, we can begin to see how Heidegger’s retrieval of Descarte’s epistemological doubt provides the basis for an existential-ontological doubt as understood in “death.”
In Being and Time, Heidegger employs an existential analysis of “death,” by which he takes to signify not merely Dasein’s “ontic” death – that is, the event by which life ceases; but rather, as the ultimate impossibility of all Dasein’s possibilities. Death, then, undercuts all Dasein’s inauthentic certitude with respect to its average-everyday existence. Death, and the accompanying mood of anxiety that precedes an authentic stance on one’s own mortality and radical finitude, dis-closes Dasein as not the ground of its existence, but rather the ground of the “not.” In coming to grips with its ownmost possibility of death, its only certainty, Dasein realizes its possibility of individuating itself by choosing among its possibilities; yet, such decisions always involve a nullification of all other possibilities, since Dasein is incapable of exercising such infinite possibility. Therefore, death opens up Dasein as the ground of a “nullity,” the “not” as possibility rooted in the existential structure of Dasein allowing its possibilities to show themselves as they are in themselves.
It is in the mood of anxiety (Angst) that Dasein is presented with the possibility of coming to terms with its own mortality and finitude. Anxiety, contra fear, is a feeling of free-floating uncanny-ness. It is not something that Dasein can overcome, for it is a part of Dasein’s structure. Heidegger describes the feeling of anxiety with the German word “unheimlich,” which translated means “un-home-like,” or a “not-being-at-home.” Authentic selfhood can only come about in Dasein’s confrontation and acceptance of its death as its “ownmost” possibility (that which can belong only to that individual Dasein) and as its “uttermost” possibility (the possibility that nothing succeeds death).
The relationship between “death” and “existential doubt” can be understood in two distinct manners.
First, the possibility of Dasein’s death as its ownmost possibility undercuts the myriad certainties and platitudes that make up its average-everyday being-in-the-world. When one experiences the grips of anxiety, one is confronted with the radical uncertainty of human existence. Existential doubt, as opposed to epistemological or cognitive doubt, permeates through existence itself: casting its shadow over all of Dasein’s existence and de-limiting its possibilities through its ownmost impossibilities. Secondly, just as Cartesian doubt is the means by which the modern philosopher is to determine the unshakable foundations of philosophical thought, so too does death/existential doubt provides Dasein with the possibility of giving meaning to its existence and its world by cutting-through the “idle talk” and “curiosity” of its inauthentic mode of being-in-the-world — opening up (dis-closing) the abyss (abgrund) of Dasein’s existence which lets meaning arise through its existence.
“To be be” is to be finite; and to be “finite” is to be cast in (existential) doubt. Only mortals are besieged by doubt; by the exhausting and inescapable uncertainties of the abyss of human existence.
In 1842/43, Kierkegaard began one of his most philosophically intriguing works – Johannes Climacus, or De Omnibus Dubitandum Ext. Though it was never completed in his short lifetime, the text itself is one of Kierkegaard’s most complex engagements with the Western philosophical tradition. The work describes itself as a ‘narrative’ – the designation of which is intended to reflect how the work differs substantially from the modern techniques of philosophical discourse. Kierkegaard’s choice of the narrative form is utilized in order to demonstrate that a life-view founded on doubt must inevitably end in despair, and thus brings into question not only the methodological doubt of Descartes as the “starting point of philosophy,” but also the drive towards systematic completion of speculative thought generally. The “task” of Johannes Climacus then is to counter modern philosophy’s chosen starting point of doubt, and bring us back to existence.
For Johannes Climacus, “doubt” refers to a kind of indeterminate, intermediary “zone,” between determinate actuality and the absolute freedom of abstraction. In doubt, the self experiences a kind of continuous oscillation between existence and non-existence (abstraction); and thus, doubt has a resistance-quality to it; a fluidity, so to speak, that departs from actuality only to inevitably return us to existence, albeit with a new set of qualifications.
Cartesian doubt, as a product of reason, attempts to take us away from engagement in existence. However, Kierkegaard notes that, for the Ancient Greek skeptics, doubt was the product of perception or interest, and thus doubt could be canceled by transforming interest (inter esse, “being-between”) into apathy, whereas apathy itself is constituted as dis-engagement (apatheia). The Cartesian stepping-away from engagement, we disclose dis-interest and dis-engagement, which in fact dissolves doubt.
Whereas dread returns the self from sensuousness to actuality, doubt performs a similar movement within the other sphere of non-existence in the aesthetic stage on life’s way. All self-becoming involves the drawing-into actuality of the two spheres of non-existence (sensuousness and abstraction), while at the same time resisting the temptation to lose-itself, and thus depart actuality, by emptying itself out into either sphere. Here, however, it must be recalled that Kierkegaard has in mind a very different point of view with respect to “actuality” than the metaphysical tradition. In The Sickness Unto Death, the pseudonymous author Anti-Climacus unraveled the traditional notion of actuality and substituted in its place a new synthetic definition of actuality as the synthesis of necessity and possibility.
Johannes Climacus serves as the paradigmatic case of what can be called “Kierkegaardian doubt.” But this peculiar “existential doubt” takes the opposite route than the more familiar Cartesian doubt. For Descartes, doubt is the starting point, which is taken into the sphere of thought itself and thenceforth infinitized. This form of doubt, which may be called reflective doubt, is the starting point of all modern philosophy since Descartes, and stipulates that all must be doubted except the existence of the thinker himself. Doubt, as understood within the strictures of the Cartesian tradition, is a product of reason, and thus does not undermine thought itself, but rather, it propels the thinker into the far-flung abyss of systematic reflection, pure thought, and mediation.
Climacus’ doubt is not a methodological doubt; he does not doubt the truth or reality of his perceptions; his is no epistemological doubt. On the contrary, his doubt is that of trepidation. For Johannes Climacus, who is a lover of the freedom of abstraction, pure and ideal thought, it is his becoming aware of the incommensurability of thought itself to the messy and unsystematic nature of actuality itself that grounds his doubt. While Johannes longs to become part of his beloved and infinite abstract thought, the same longing that plagues all of modern philosophy, it is doubt that reminds him of his non-ideal existence; of existence as such.
It’s at this juncture that the essential difference between Cartesian methodological doubt and Kierkegaardian existential doubt makes itself felt. Whereas the former is a disinterested and abstract relation within thought itself, the latter is always already interested, and therefore, brings the thinker back from abstraction into existence. Thus, in doubt’s interplay between actuality and ideality (existence and non-existence), existential doubt is a mixed, never wholly contained within any given sphere, or relation.
Upon thinking the difference between Cartesian doubt and existential doubt, Johannes begins to question how doubt is possible in the first place. He invariably comes to understand doubt as that which provides the means for grounding thought in existence – in stark contrast to the metaphysician, for whom doubt is the means by which thought escapes existence. In virtue of his doubting, Climacus is brought more closely into existence, but he also brings his thoughts with him – while at the same time transforming his own relation to actuality. Thus, the artificial “gulf” between the existing thinker and his thought-world, the product of Cartesian metaphysics, is bridged by virtue of existential doubt, which eradicates this paradoxically fundamental, but also derivative, dichotomy responsible for this difference. For Johannes, his doubt is not disinterested speculative thinking; but on the contrary, it is always interested.
Thus, it is easy to see the inter-relationship between Cartesian-reflective doubt and the misconstrued conceptions of the individual indelibly tied to modern thinking. To begin with, the uniquely modern conception of the individual contributes to a false conception of the universal or the objective as an inaccessible realm of abstraction for which, save for thought itself, the individual was cut-off. Under these circumstances, Cartesian doubt has the tendency to eliminate the particular and thus de-situate the thinker from his own concrete situated-ness. Thus, the Cartesian thinker is always a thinker who thinks from “nowhere.” Existential doubt, according to Johanness, takes as its starting point the project of abstract thinking, pure thought, and returns us to situated-ness, to the particularity of the individual thinker for whom doubt is always already interested.
Working in combination, it may be said that reflective (Cartesian) doubt elevates the individual – moving him up into the ethereal domain of pure thought itself, while, existential doubt drags him back to his own existence, for whom he is always concerned, and which he may never rid-himself of, no matter how hard he tries.