Indexes are empty signs. They merely show existence – “there”, “now”. The power of the index is denotative. It compels us to draw our attention to a specific object, here and now. The index only exists when it is connected with the individual object. Animals use their excrement as a message to circumscribe the space they have allowed to themselves. To men as well any sign is, before anything else, a stain, a signal. A scratch in the paintwork or a stain on the wall are features we attribute to someone: «Who did this?»
The thumb mark the potter left imprinted in the vases he sculpted surprises us. Whether it is the memorial of the Pharaoh’s campaigns or a simple graffiti on a wall, the inscribed/written stands the test of time through its own materiality. By definition, in printing nothing separates thing and object: in a death mask, the mould preserves a shape from which the flesh has disappeared, but which imposes itself, although it might be replaced by any other matter. The imprint is seen as a testimony, as evidence and individual signature. In the case of the mask, the face that is moulded and the mould must be current (the former) and potential (the latter), to function as a sign, through interpretative processes, reminiscence and testimonial strategies, etc. The imprinting of patina (copper carbonate formed in bronze statues and medals, an earthy concretion on ancient marble) is inscribed on a surface by means the traces which have accumulated through its use. Patina is a trace of the enunciative praxis. It is the perfect example of a non-subjective enunciation index.
In Peirce’s theory, this category encompasses the intentional indexes which are present in human communication. Sebeok calls them designators. Peirce defines index as opposed to symbols and icons as a category which includes both natural and conventional signs. A sign vehicle is an index if it is “really affected” (Peirce § 2.248) by its referential object. “The index is physically connected with its object: they make an organic pair” (§ 2.299). Peirce included in the index class a clepsydra, a photograph, a pointing finger, a scream. The index is a fragment of an object or in contiguity to it, part of the whole or used for the whole. In that sense, a relic is an index: the femur of a saint is the saint. Or a footprint in the sand. Besides, Peirce uses the term to signs as diverse as an imprint, a thermometer, a thunder, the word “this”, an index finger, a photographic image – in such a way that the concept caused a certain confusion. Indexes and symptoms correspond to the ancient class of natural signs. The index class is usually defined as opposed to the symbol class. In Peirce’s taxonomy of signs, the power of the index is denotative. It compels us to draw our attention to a specific object, here and now (Pierce 24). The author defines index as “effectively, and in its individual existence, connected with the individual object” (Peirce 251), even if it does not shed any light on the nature of its objects. It has no cognitive value: it merely shows something like “there”. The “real” referenced by the index is therefore not the “real” of realism. It is a coarse, opaque fact; pure indication. For Didi-Huberman that is the significance of the small, irregular, localised stain, of what is supposedly the face of Christ imprinted on the sudarium in Turin. Indexes are characterised by a certain singularity; they always refer to individuals, to singular units. They depend upon a given contingency: the wind that blows at a certain moment and in a certain direction, a foot that has left a footprint in the mud at an exact spot or the camera that shoots at a precise moment. As with icons, indexes have no similarity with their objects, even though they cause them directly. This is due to the fact that indexes are void of content. An index finger, for instance, designates something without describing it (“The index does not state anything; it just says: “There” . It draws attention towards an object by “blind compulsion” (Collected 161). As with icons and symbols, which are associated according to their similarity or intellectual operations, the index’s work is associated according to contiguity (the foot touches the floor and leaves a trace, the wind pushes the weathervane, the index finger shows a spot). The specificity and singularity which are associated to the index are clearly shown in the designation of demonstrative pronouns (“this”, “that”). “In language all that is related to the dixis is an index: words such as I, you, here, now . R. Jakobson calls dictic shifters because their reference is totally dependent on the speaker’s situation. Resnikow defines index as a natural sign based on a “natural connection” between vehicle sign and referent (1964, p. 138-39). On the other hand, U. Eco divides the natural signs class into symptoms and indexes (Eco, 1973b, p. 67). Both are defined according to their contiguity relation. Husserl defines indexes are natural or artificial signs produced unintentionally (1900, p. 31). “This” is void of any content and merely designates a specific singular object or situation, when language seems to land, to adhere, to the present reality of speech. For Peirce, the iconicity of the photographic image is reduced by the complete adherence of the sign to its object. Photography and film seem to be excellent examples of the sign systems that define icons, indexes and, up to a point, symbols. Although they are iconic – as they exist in similarity with the object – they are also indexical, as there is an existential connection between the photographic image and its object. And, because both photography and film resort to language, they invoke the symbolic field. Peirce seems to have situated photography as being primarily indexical, subordinating its iconic dimension to secondary status (Collected 159). The index’s distinctive characteristic is its physical or existential connection with its object, which, in the case of photography, gives cause to an iconic image. The index, as described by Peirce, is frequently linked to two contradictions or, at least, two incompatible definitions. First, when the index is exemplified by imprint or the photographer, it is a sign that may be described as a trace or an imprint of its object. Something of the object leaves a material connection between sign and object – the reproductibility of a moment gone by. The trace has not evaporated at the moment of its reproduction; it stays there as a witness to its anteriority. The index as dixis – the index finger, the language’s “this” – are linked to an undeniable presence. There is always an abyss between sign and object; touch is merely figurative. Out of these two dimensions of the index, the latter frequently falls into oblivion. Only the former definition – index as imprint or trace – seems to correspond to the cinematic image. The index finger, which shows up in the language’s “this” incarnated in the ideal of indexicality, is pure shape. The void of the significant “this” clearly contrasts with the abundance of the cinematic image, with its inevitable iconicity. An index does not stop being an index even if the interpretant is missing, whereas the existence of its object – the illness to a symptom, for instance – is semiotically necessary to it. Peirce shows symptom as a paradigm of the index because the symptom semiotises evil in action: drama. It is the Greek word for crime and rite. If all contact appeals to its founding act – through an indiciary relationship -, thus all act appeals to the actor’s first name (Peirce also mentions the first name as a paradigm of the index, because it is linked to an absolutely specific subject. Besides, the first name is also a «legisign»: a sign that legalises its relation.