Heidegger notes that our primary interaction with beings[4] is through use or by communication if human beings are concerned. Dreyfus describes this interaction as ‘skilful engagement’ (Dreyfus, 1991). Dreyfus and Wrathall (2005, p. 4) in their introduction to a collection of essays on Heidegger write, “we first encounter worldly things as available.

Something is available when (1) it is defined in terms of its place in a context of equipment, typical activities in which it is used, and typical purposes and goals for which it is used, and (2) it lends itself to such use readily and easily without need for reflection. The core case of availability is an item of equipment that we know how to use and that transparently lends itself to use”. For Heidegger, all human activity is located in vast, inter-related array of tools and equipment. For example, I am writing this at my desk, in my office sitting on a chair. On the desk is my Apple™ iMac, to the right of which is a wireless mouse (I am right-handed). Immediately before me is a wireless keyboard, to my left is a coffee cup, a notebook, a book on Heidegger, and a pile of academic papers. By the above definition, all of these items are available to me, as they are proximal and ready-to-hand and comprise one of my working environments. However, in addition to these physically proximal entities, I have a high speed Internet link which (by way of a click or two) connects me to online databases located on other continents. I also have access to a range of network services located through the University – but exactly where I really have no idea. So, readiness-to-hand is a matter of experience, or of how I encounter the world rather than location in physical space. Indeed readiness-to-hand is also a very good description of the affordances available to Dasein (Gibson, 1986).
This Heideggerian perspective moves us away from thinking in terms of listing the discrete properties of things, to how we encounter these things as tool-beings (Harman, 2002). Re-casting this slightly, we can say that we encounter the world as a network of inter-connected affordances (Turner, 2005). Gibson describes an affordances in a similar kind of way, for example, when he writes “An affordance cuts across the dichotomy of subjective-objective and helps us to understand its inadequacy. It is equally a fact of the environment and a fact of behaviour. It is both physical and psychical, yet neither. An affordance points both ways, to the environment and to the observer” (Gibson, 1986, p.129). Thus affordance is not a property of a tool but how we encounter that tool. While this all appears rather functional, and rather confined to manual labour, tools for enjoying ourselves and for having fun are no different. However, since Gibson first introduced the concept, it has been developed in a variety of ways particularly by ecological psychology (e.g. Warren, 1984; Turvey, 1992; Stoffregen, 2000) and human-computer interaction communities (e.g. Norman, 1988; 1999; Gaver, 1991; 1992; de Souza, 1993; de Souza et al., 2000 among very many). Hartson (2003), for example, has proposed a four-fold division of affordance for the purposes of designing for interaction. These four categories are (a) cognitive affordance; (b) physical affordance; (c) sensory affordance and finally, (d) functional affordance. This four-fold classification maps onto corresponding functions: for example, physical affordance is synonymous with utility, while sensory affordances include such things as colour and contrast.
Affordance also appears in the academic reporting of anthropology, for example, Cole (1996) identifies a range of affordance offered by a variety of mediating artefacts including the life stories of recovering alcoholics in Alcoholics Anonymous meetings (affording rehabilitation), patients’ charts in a hospital setting (affording medical diagnosis) and poker chips (affording gambling). Cole notes that mediating artefacts embody their own “developmental histories” which is reflects their use.
Finally, there is also substantial evidence from studies of the neural basis of perception and action, for example, positron emission tomography has shown that those parts of the brain responsible for motor representation are activated in response to the perception of the affordances of objects. Grèzes and Decety (2002, p. 212) concluding that “perception of objects automatically affords actions that can be made towards them” – cf. Freeman. It may be that availability has its origins with the ways in which we first encounter the world. Although Heidegger does not address the issue of our corporeality or embodiment, it is evident that we first encounter the limits of the scope of what is available, proximal and handy by way of our bodies. This progresses from encountering our own hands (through, for example, sucking our thumbs) and the body of our mother to all manner of external objects (beings) to the internalisation of these actions to form what we experience as cognition – if Piaget is to be believed. So, it is likely that embodiment is at the root of what we find available.

So far we have suggested that two of the requirements of witnessing are complementary: the readiness to encounter and the offers to encounter[5] presented to Dasein. In the next section we consider the issue of the representation of the witnessed event.

Note 4: Heidegger’s ontology requires us to regard all things in the world as beings–e.g. chair-beings, book-beings, macbook-pro-beings, pencil- beings, cup-of-coffee-beings. While this is, to most people, unfamiliar it does remove the fundamental Cartesian assumption of subject and object. Instead, we encounter other beings but this is not to suggest that these beings have intelligence or sentience but that an everyday ontological examination of chairs would be into their chair-ness for me. The everydayness of a chair is its availability for sitting on, or standing on, or for barricading a door with and so on.
Note 5: Lewin (1936) referred to affordances as Aufforderungscharakter or invitation character.

Phil Turner