Andy Clark & David J. Chalmers, The Extended Mind, ANALYSIS 58: 1: 1998 p.7-19

Synopsis

Main question: Where does the mind stop and the rest of the world begin?


First case study:
An human agent playing TETRIS (in some future), to assess if a piece will fit or not in a slot, could:

1. mentally rotate the object;
2. use a key to rotate the object on the computer screen;
3. use a neural implant able to produce the same rotation as case b), but this time activated by his thought and visually reproduced on his retina.

The three cases are very similar: 1) and 3) are clearly internal, 2) is external and distributed between subject and computer, but:

If, as we confront some task, a part of the world functions as a process which, were it done in the head, we would have no hesitation in recognizing as part of the cognitive process, then that part of the world is (so we claim) part of the cognitive process. Cognitive processes ain't (all) in the head!

Which is what Andy Clark in “Memento's Revenge: Objections and Replies to the Extended Mind" to appear in R. Menary (ed) Papers On The Extended Mind call: Parity Principle.


At this regard is important the distinction:
epistemic action <--> pragmatic action
Epistemic actions alter the world so as to aid and augment cognitive processes such as recognition and search.
Pragmatic actions, by contrast, alter the world because some physical change is desirable for its own sake.
Kirsh, D. & Maglio, P. On distinguishing epistemic from pragmatic action. Cognitive Science 18:513-49. 1994

So:
In these cases, the human organism is linked with an external entity in a two-way interaction, creating a coupled system that can be seen as a cognitive system in its own right. All the components in the system play an active causal role, and they jointly govern behaviour in the same sort of way that cognition usually does. If we remove the external component the system's behavioural competence will drop, just as it would if we removed part of its brain. Our thesis is that this sort of coupled process counts equally well as a cognitive process, whether or not it is wholly in the head.


C&C call their position Active Externalism.

This externalism differs greatly from standard variety advocated by Putnam (The meaning of `meaning' -1975) and Burge (Individualism and the mental.1979),
In Putnam’s example the relevant external features (water = H2O or water = XYZ – Hearth /Twin Hearth) are distal and passive. This is reflected by the fact that the actions performed by me and my twin are physically indistinguishable, despite our external differences. In the cases we describe, by contrast, the relevant external features are active, playing a crucial role in the here-and-now.

Could be possible to refute this kind of externalism identifing the cognitive with the conscious, as seems far from plausible that consciousness extends outside the head. But not every cognitive process is a conscious process. More interestingly, one might argue that what keeps real cognition processes in the head is the requirement that cognitive processes be portable… the trouble with coupled systems is that they are too easily decoupled. But this is a contingent aspect. The real moral of the portability intuition is that for coupled systems to be relevant to the core of cognition, reliable coupling is required.

Language appears to be a central means by which cognitive processes are extended into the world.

So far we have spoken largely about "cognitive processing", and argued for its extension into the environment. Some might think that the conclusion has been bought too cheaply. Perhaps some processing takes place in the environment, but what of mind? Everything we have said so far is compatible with the view that truly mental states - experiences, beliefs, desires, emotions, and so on - are all determined by states of the brain. Perhaps what is truly mental is internal, after all?

We propose to take things a step further. While some mental states, such as experiences, may be determined internally, there are other cases in which external factors make a significant contribution. In particular, we will argue that beliefs can be constituted partly by features of the environment, when those features play the right sort of role in driving cognitive processes. If so, the mind extends into the world.


Second case study:
(to address the portability issue and to extend the treatment to the more central case of an agent’s beliefs about the world.)

• Inga hears of an intriguing exhibition at MOMA. She thinks, recalls it's on 53rd St, and sets off.
• Otto suffers from a mild form of Alzheimer's, and as a result he always carries a thick notebook. When Otto learns useful new information, he always writes it in the notebook. He hears of the exhibition at MOMA, retrieves the address from his trusty notebook and sets off.

Just like Inga, Otto walked to 53rd St. because he wanted to go to the museum and believed that it was on 53rd St (even before consulting his notebook, unless we don’t consider as beliefs only the current ones, but then also Inga didn’t belief that the MOMA was in 53th street before fetching this information from her memory). Otto’s long-term beliefs just weren’t all in his head.

To be included in someone cognitive system his beliefs must be:

1. constantly available and used,
2. easily accessible,
3. immediately believed (not subject to critical scrutiny)

What about socially extended cognition?
Also in this case it seems there are not valid reasons to exclude someone else believes (I’m constantly surely rely on) in my believes.
In this case languages play a central role. Without language we will be closed in a Cartesian solipsism where all relies on inner processes. Thanks to language we can partially spread this burden into the world. Language, thus construed, is not a mirror of our inner states but a complement to them. It serves as a tool whose role is to extend cognition in ways that on-board devices cannot. Indeed, it may be that the intellectual explosion in recent evolutionary time is due as much to this linguistically-enabled extension of cognition as to any independent development in our inner cognitive resources.

Finally, also our self image should be revisited. As our self goes beyond our conscious states, so could go beyond the border of the skin.