In beginning his lengthy phenomenology for identifying the pathway in which Geist will realize itself as Absolute Knowledge, Hegel begins at what many considered the most basic source of all epistemological claims: sensual apprehension or Sense-Certainty. Though the skeptical tradition took this realm as a jumping-off point for making defensible epistemological claims, Hegel sees in the sensual a type of knowledge so general and abstract as to be entirely vacuous. Focusing on the principle that anything known in the Scientific sense must be communicable, through language or its approximations, Hegel shows that whatever the sensual purports to know is inherently incommunicable and therefore cannot represent true knowledge.
An important precondition for Hegel's examination of the sensual is his caveat that sense-certainty must not use complex concepts of any kind to express that which it knows. In this sense, Hegel treats sense-certainty as the realm whose truth is expressed as pure being or ISNESS, as opposed to mediated forms that understand ISNESS in a wider context of meaning (Hegel, 91). By insisting on this limitation, Hegel treats sense-certainty as stripped down to bare assertions of sensual experience, allowing the phenomenologist to examine the sensual based solely on what it is capable of showing us on its own. Indeed, it is this litmus test of self-sufficient communication that sets the stage for Hegel to return sensuality to the universal conceptual framework that supports it once it has been seen to fail in its own right.
In the first stage of his examination of what the sensual might offer in the way of knowledge, Hegel examines the object apprehended by a sensing consciousness. This is not to say that Hegel neglects the mediating role that the subject plays in this process but only that he examines the case where the mediating subject is inessential in that even if it were not to know the object, the object would still have a reality as a pure being or ISNESS (Hegel, 93). In this dialectic of the object, the apprehension of the object as being can occur in two indexical cases, the first as a NOW (temporal indexical) and the second as a HERE or THIS (locational indexical). In both cases sense-certainty's attempts to indicate the object which it has apprehended as the repository of knowledge fail because, upon examination, both indexicals are shown to be entirely vacuous. Hegel's' proof of the critical limitations of these terms is based on the idea that both NOW and THIS cannot of themselves differentiate an actual location or time without the support of more complex assertions, namely NOW as differentiated from all other NOWS or THIS as differentiated from all other THISES. As a result, the NOW and THIS that intend to refer to particular objects instead refer to the universal cases of NOWNESS and THISNESS, cases which contain a knowledge that is no real knowledge at all (Hegel, 95-99). Hegel's most cogently outlines the failures inherent in the dialectic of the object by approaching the NOW and THIS as if they were written down on paper, reintroducing his theme of linguistic communication as prerequisite of real knowledge. As we imagine these terms written down, we quickly see that NOW alone on paper cannot differentiate itself from other NOWS (and the same for THIS), so that the NOW of today is equal to the NOW of tomorrow and therefore both are meaningless (Hegel, 95).
Realizing the abstract generality of undifferentiated objectness located in the dialectic of the object, sense-certainty attempts to resolve this failure by referring instead to the subject that senses a THIS or NOW, as if to fixate in the mediator what was so elusive in the object being mediated. Though the focus has changed in this approach, in the new dialectic of the subject we once again experience sense-certainty's inability to communicate once stripped of its conceptual framework. In this case the failure of NOW and THIS is replaced by the failure of 'I' which, intended as a particular, can instead only function as a universal reference to all 'I's. Just as in the dialectic of the object, sense-certainty as the realm of raw being or unmediated sensual experience cannot differentiate this 'I' from another 'I' without using the more complex, (and therefore off-limits), construction of "this 'I' as differentiated from all other 'I's". Instead of a meaningful reference to a particular subject that has experienced the original object in question, we are left with the universal case of 'I'NESS, which is of no use in apprehending the identity of the subject which might have knowledge of the object of sensual experience.
Having experienced the dead-ends found in the both dialectic of the object and the subject, Hegel's final attempt to ascertain the potential of sense certainty is to unify these two attempts, approaching the issue as a dialectic of the totality of subject and object. Initially, this approach solves the problems found in the first two dialectical stages in that the totality is no longer concerned with other HERES, THISES or 'I's, since in the totality each THIS or HERE is directly linked to a specific I and vice versa. This is what Hegel means by calling the totality "self identical." (104) Owing to this nature of self-identification, we now must treat the totality as one instance, a treatment that Hegel suggests could be made through a moment of ostension or pointing.
In the moment of ostension, however, sense-certainty's inability to utilize a complex framework of meaning once again dooms it to communicating only the most vacuous or general knowledge about what is in reality a particular experience. Hegel breaks this third and final failure into two pieces and, though his construction is more complex than in the first two dialectics, there remains a strong similarity to the failures of stage one and two. In the first failure of the totality, Hegel notes that our referral to the totality of subject and object as a NOW is only truly meaningful if we can place it in the context of all NOWS past and present. Without this framework to aid us, the NOW of totality is, immediately upon ostension, a "has been," which is the negation of being (or ISNESS) that sense certainty was concerned with in the first, or as Hegel says: "and it was with being we were concerned" (Hegel 106). In a more complex framework the NOW of ostension could become an IS after moving from ISNESS to WASNESS (or HASBEENNESS) and then back to ISNESS as a function of all BEFORES, AFTERS etc., though Hegel notes that this NOW as reflected back into itself is different that the unmediated NOW with which we began originally (107). In any case, the negation of the negation of NOW is a complex process that is far outside the realm of sense certainty, a stark contrast to the vacuous "has been" supplied to us by sense-certainty's moment of temporal ostension.
Hegel makes a similar claim for an ostension of THISNESS, and here his observation brings to mind Wittgenstein, who reminds us that ostension outside of a framework of meaning allows for only the universal case of THISNESS. In other words, the THIS or HERE would only be meaningful as they relate to behind, above, below etc. (Hegel, 108) Like NOWNESS, THISNESS would come to mean something real only after passing through both its negation (NOT THIS) and the negation of the negation (NOT NOT THIS). Without this complex relational structure, the pure moment of ostension is of no real use other than to indicate a generality that is entirely without meaning, a universal THISNESS that has no context in which to communicate.
Having failed in all three stages of apprehension (object, subject and totality), Hegel is forced to admit that the seemingly rich world of sense certainty is of no use in providing comprehensible knowledge of a particular sort. After derisively comparing those believers in sense-certainty's capabilities of Knowledge to animals and Eleusinian devotees, Hegel returns to his theme of Knowledge as communication through language, insisting that to make a claim about the knowledge contained in sense-certainty is: "not to know what one is saying, to be unaware that one is saying the opposite of what one wants to say" (Hegel, 109). Left with the thingness or being of sense-certainty as an undifferentiated, universal and unintelligible generality, Hegel concludes by abandoning sense-certainty in its own right and moving on to the next level of complexity, namely perception, or thingness as understood the properties that define it.
Hegel, G.W.F.. Phenomenology of Spirit Oxford University Press: New York, 1977.