This is most definitely a work under progress. These thoughts came from criticising Anthony Chemero’s “Radical Embodied Cognitive Science, ch. 7 “Affordances etc.” and concludes with the (in)famously ambiguous quote from Gibson on what affordances are defined as.
If affordances are defined as the relation between (or, the relation between is a part of the definition). Then an object need not exist if an agent is not perceiving it. It can, but it needn’t. This will incorporate idealism in full or in part and this is unsatisfactory.
If affordances are defined as the individual ability of an agent and the property of an object, then neither are necessarily coupled. Also unsatisfactory.
However, if abilities and properties are given a compatibility value (a, metaphorical, mathematical/numerical range), which, if in perception of each other are [also] within each others’ range and can thus be combined/actualised/realised. Then, if this is what we wish to call an affordance, is inherent individually in the object and the agent (and thus exist without the presence of each other) but can only be actualised in presence of each other (or by other agents/objects within the same range). Thus, an affordance is neither solely subjective, nor objective, at the same point in time. Or both, if you will. (I hope I got at least a chuckle from this rephrasing of Gibson.)
This view is compatible with evolutionary aspects, ecological aspects but is not selectionist [things Chemero makes a good point of what we should want]. In short and simple, there are many, albeit finite, number of affordances and those that have been directly linked to survival and reproduction (which are temporally and situationally dependent, although this specific aspect falls under biology to explore/have explored) have thus determined our phylogenetic development.
I suggest following terminology (although I have to admit that I am slightly confused by all the existing definitions and so reserve myself for the mistake of reifying someone else’s definition. Should this be the case, I apologize and will credit you accordingly)
Actualised: object/agent in a physically coupled, mutual, dynamic relationship that is temporally bound. (Temporally bound refers to that actualizations of affordances do not last forever, in the most extreme case, we die, but, the temporal aspect is necessary, for development, evolution and dynamicism more generally. Although it can be argued that someone else can keep actualizing what I did before death, this is still another instance, another coupling, that can be simultaneous to my coupling. This thus also holds for collective behaviour.)
Realised: object/agent in a perceptually coupled, mutual, dynamic relationship. (Perceptually bound, spatially bound, geographically bound. Referring to the necessary perception of the object and its affordances and (but not necessarily) the agents affordances and the compatibility range of both. Basically, we need direct perception, and perception at all to be able to realise that there are objects at all etc..)
Both these terms are necessarily physically bound, both by their individual physical properties (body of the agent and shape, density etc. of the object) and the physical constraints of the environment (gravity, exemplifying a more so global constraint, and situationally specific things for example social norms, etc.).
This, allows us realisations in absence of the relevant object but actualizations only in presence. It also allows us to avoid Evil Philosopher arguments, examples of cases when we don’t actualise although we can and failing an attempted actualization.
Arriving at the terribly mundane conclusion that we can interact with things when they are there and they are retained when we are not. To be continued… …probably in my master thesis…
I should be quick to add that 'relationship' in the two definitions does not bear on the definition of affordance in the sense that affordances are, ontologically, neither, rather they should be seen as epistemological concepts in their relation to affordances. Excuse the confusion.
Also, there is a non-necessary but mutually informative relationship between actualisation and realisation, forming, on the whole, a dynamical system. The definition of affordance as in the post, also places affordances in monist materialist/realist friendly terms, avoiding invoking neutral monism/dualism.
In fact, I wonder if not inherent properties in the environment are necessary if we wish to marry embodied cognition with evolution and biology. The environment was/is already there when we enter/ed it, had it not lent itself to be perceived in more than one way then the biological cost of evolving and maintaining (offsetting its survivability/reproducability value) more senses than one, then it is unlikely we would see the plethora of senses that animals use to perceive the environment. Of course this is hind-sight, had we been single-celled organisms at the dawn of life, we would probably have "seen" things differently (ha.. ha..).
The above comment however doesn't mean we are the pinnacle of evolution or development, we may evolve to pick up another sense, wholly different to existing ones (I would hate to be accused of a frame-of-reference fallacy), but, it will need to provide an advantage in survivability/reproducability large enough to offset the already existent senses. However, temporally and biologically, the environment is in a phylogenetic sense, necessary (but not sufficient, for it to be both we need to include bodily processes such as genetic change over generations, and behavioural processes such as successfully implementing them in the environment). On the flipside, we can have as much genetic change imaginable, but, for any change to manifest it needs to enhance survivability and reproducability and it does this necessarily dependent on the environmental pressures. These pressures determine in part the abundance of affordances, but pressures are not affordances in themselves.