Does intentionality admit of naturalistic explanation?
Yes, it does. At least it does if one adopts physicalism. It doesn’t, of course, if one adopts anti-physicalism. In other words, the answer one provides will depend on one’s prior attitude towards physicalism.
The term “intentionality” refers to the phenomenon that mental states/attitudes/concepts are about, are directed on, or represent other things. There is something that I affirm, deny, interpret, understand, believe, hope, wish, like, love, hate, (and according to some, perceive or sense), and so forth. “Intentionality” is this rather vaguely characterized notion of “aboutness”. The modern use of the term was initiated by Brentano towards the end of the 19th Century. He claimed that every mental state has intentionality and is directed towards an “intentional object”. In modern philosophy of mind, is it hotly debated whether this notion of “aboutness” is a necessary and / or a sufficient condition for things mental. Some claim that only things mental can have this “aboutness.” Others claim that non-mental (i.e. physical) things can have the same sort of “aboutness”. The division between views matches the division between physicalism and anti-physicalism.
There are, of course, many purely physical things that have an “aboutness”. Maps, photographs, sentences of a language, and so forth, are all about something. But the anti-physicalist draws a distinction between “intrinsic” versus “derivative” intentionality. Intrinsic intentionality is intentionality that is not derivative. An object has derivative intentionality when its “aboutness” relies on the interpretation of something outside that object. So a sentence of a language, for example, is about something only because something outside of it (a mind) provides that aboutness. The anti-physicalist argument is that only mental states have intrinsic intentionality. Philosophers arguing in this direction include Jerry Fodor, John Searle, Fred Dretske, Tyler Burge, Saul Kripke, among others.
In contrast to this view, consider the Martian Spirit rover. It has a panel of photocells fixed to its back. To angle its panel of cells to maximize power acquisition, the drivers sitting at JPL in Pasadena had to drive the rover up the side of a hill. Suppose JPL builds a Spirit2 rover that has two advances. One is a panel of solar cells that the rover can tilt and swivel on its own — it has a program module specifically programed to do so when provided with a position to point to. And the second is a skycam (with its associated analysis software module) that tells that solar panel program module where the sun (the brightest spot in the camera view) is located. Now Spirit2 can maximize its power acquisition without the involvement of the drivers at JPL. The message from the skycam analysis program module to the solar panel manager program module is clearly “about” the power maximization coordinates. The intentionality of this “aboutness” does not rely on the interpretation of something outside of it. The drivers at JPL need have no inkling about the messages passed between the two program modules. If this counts as “intrinsic” intentionality, then the physicalist case is made.
But the general reply of the anti-physicalist is that the entire Spirit2 rover is a device designed by a mind, and hence derives any intentionality of its parts from the intrinsic intentionality of the designing mind. But this response runs into the counter argument, offered by the likes of Ruth Millikan and Daniel Dummett, among others. We human beings are but a device designed by “Mother Nature” — otherwise known as the blind watchmaker, or the processes of evolution. According to Dawkins, we (including our minds) are the result of the purely physical processes of evolutionary selection, “designed” for the purposes of ensuring the survival and proliferation of our genes. And no one suggests that “Mother Nature” (in the guise of evolution or our genes) has a mind, or intrinsic intentionality. If we are the results of a purely physical process of evolution, and it is admitted that we have intentionality (intrinsic or derivative), then the physicalist case is made.
If this is the case (and a Designing Intelligence is not smuggled in), then where is the principled difference between us, and our “intrinsic” intentionality, and the Spirit2 rover and its “derived” intentionality? If we (our minds), are an artifact designed by the physical processes of evolution, and do have intentionality, then intentionality obviously admits of a naturalistic explanation. If intentionality does not admit of a naturalistic explanation, then we (at least our minds) are not a result of the physical processes of evolution. The anti-physicalist must provide something extra.
Either way, the answer to the title question will depend on one’s prior commitment or opposition to physicalism.