(Continuing reflections on the topic of "explanation"....)
The machine hasn't fared well as a cultural icon for the last while. From the image of the dehumanized, roboticized workers in the vast urban machine of Fritz Lang's Metropolis to the metallic death's-head horrors of theTerminator series, the mechanical in film and culture generally has been portrayed as something deeply antithetical to the human. No doubt the antipathy goes back at least as far as the coal-fed steam engines that powered Blake's "dark, satanic mills". It's as though there's an undercurrent of fear running throughout technological culture that we ourselves are in danger of turning into machines. Little wonder, then, given that sort of context, that there might be some serious resistance to the idea that, in fact, we already are machines.
But what exactly is a machine in the first place? Apart, that is, from a lifeless and soulless artifice, the very embodiment of the anti-human? In one sense, a machine is just a tool, as evident in that "simple machine", the lever. But there's a different, though related, sense, in which a machine is any system involving a number of parts, assembled in a particular manner, connected by determinate or causal processes, and capable of performing some function. As such, the idea of the machine or mechanism applies not just to artificial constructions but has become a general model of explanation for natural processes of any kind -- if we can provide an account for any phenomenon in terms of purely causal interactions between its parts or components, then we can say that we have provided a mechanism for that phenomenon. And with that we will have gained a metaphorical but nonetheless very effective "lever" for it, or a way of bringing it under our control. The idea of seeking out the "mechanisms" of natural phenomena lies at the heart of the technological or industrial civilization that has transformed the earth.
This idea wasn't always so prevalent, however. Just as the extension of the idea of the simple tool provided one explanatory model for natural phenomena, so an extension of a concept based upon our own social interactions provided another: this is the notion of "agency" as an explanatory model. At the basis of this notion is the idea of will or purpose, which plays an explanatory role parallel to that of cause in mechanism. Once, it was common to view such an animating will, instantiated in God or gods or spirits, as the explanation of virtually all natural phenomena of any significance, and we can still see a vestige of this in the tendency to speak of natural disasters as "acts of God", for example. Note that this notion of agency as an explanatory model offers nothing like the kind of effective control over phenomena that mechanism does -- instead, the forces behind events could only be flattered or appeased, with always uncertain results.
About four or five hundred years ago in Europe, however, this model began, slowly but implacably, in one field of phenomena after another, to be replaced by the mechanistic model. One of the last of such areas, and one which looked to be particularly resistant to the advance, was that of living organisms, which seemed, almost by definition, to exhibit the sort of will or purpose that was the essence of agency. But, of course, the last fifty years or so have witnessed perhaps the greatest success of the mechanical explanatory model yet, with the discoveries of the various mechanisms underlying the phenomenon of life itself*. (It's worth pointing out that living processes often depend upon randomness rather than strictly determinate causal sequences, but that such "stochastic" processes are nonetheless sufficiently reliable on a statistical basis to qualify as mechanisms.) So by now, the notion of agency as an explanatory model has been pushed back to the social and psychological arena in which it first arose, and is under some pressure there.
For reasons that I've already touched on -- having to do with an inherent indeterminacy in cultural self-knowledge -- I think agency is secure in this arena, finally, against further encroachment. In this more limited field, agency really serves more significantly as a moral concept than as an explanatory one in any case (though of course it can also play a different kind of explanatory role to some degree as well). In this, it addresses directly much of our fear of the machine, since what really arouses concern, in this contest between models, is not our humanity per se(except in a broad or metaphoric sense) but rather our status as moral agents. At some point in our future, after all, an expanded cultural ecumene might well include actual machines (e.g., robots, androids, etc.), not to mention aliens, speaking animals, or what have you, and they too would be simply incorporated as fellow agents into the moral realm that communication engenders. What repels us, quite rightly, about the image of ourselves as machines is the thought that it seems to turn us into mere tools or instruments (in the hands, implicitly, of another will or agent) -- but that is something that mechanistic explanation in itself is simply unable to do (though some ideologies have thought they could, and tried, with horrifying results). It's not the machine that we should fear, in other words, nor mechanism as an explanatory model, both of which have brought immense benefits and opportunities, and have, if anything, on the whole enhanced rather than diminished our humanity. It's, as always, the tragically mistaken uses to which they're put, but to which we can, and must, refuse. Understanding that can make the enquiry into the mechanisms even of consciousness and culture not just a useful, but an entirely human undertaking.
*Including, in just the last twenty or so years, the mechanisms behind the enormously complex processes of developmental biology -- this is a plug for a fascinating book I'm in the middle of, Endless Forms Most Beautiful by Sean B. Carroll.