How can a single thing be all of physical, mental and abstract? In particular, how can languages and linguistic items be like this? The answer hinges on a bunch of disambiguations.
There are two relevant senses of ‘physical’. One amounts to something like: an object quantified over by sciences like Physics and Chemistry. Put epistemically, something is physical only if such a science can “see” it. Crucially, many objects of immediate everyday experience are not “physical” in this sense. Neither weeds nor clouds would count. The other relevant sense of ‘physical’ is something more like: an object with extension, shape, location in space and time, and (possibly) secondary properties like colour, odour, and taste. In this sense, weeds and clouds are physical things. (Interestingly, not only are there “physical” things in the second sense that aren’t “physical” in the first, but the reverse also appears true: the wave function and loop quantum gravity, for instance, don’t look to be “physical” in the broad, everyday sense.)
In a similar vein, there are two relevant senses of ‘mental’. One is: an item inside the individual mind – in the way that a pain, hallucination or tickle is. The other sense at issue is the neo-Kantian one of being individuated in terms of mental states. Something “mentally conditioned”, to deploy a purposely vague term. An example. It is a familiar philosophical confusion to say that green or bitterness are in the human mind. Though an image or memory of a bitter green apple may be inside my mind, no bitter green apple is to be found therein. Bitter green apples are not themselves inner mental items, as pains are: they are concrete material things. And yet, to use the philosophical jargon, bitterness and green are both widely regarded as response-dependent secondary qualities: that is, what makes an object bitter or green is the kind of mental episodes it can give rise to. In this highly specialized sense alone are they “mental things”.
Lastly, in one philosophical usage, ‘abstract’ is synonymous with ‘Platonic object’, and the only instances are numbers and other logico-mathematical things. What is most characteristic of Platonic objects is that their properties are wholly independent of the physical world in general, and human activities in particular; and their nature is not discovered empirically. There is another sense of ‘abstract’, however, namely things which are not inside the mind, yet are not concrete particulars either. Neither fish nor fowl. Let me coin the term ‘abstractish’ for these. Examples include the American Constitution, Beethoven’s 5th symphony, and the 2009 Ford Focus (the model, that is). These do depend on us, and must be discovered empirically; yet they aren’t like tickles, and they aren’t like rocks either.
Can an object be inside the mind, a posit of a physical science, and a human-independent Platonic object? Of course not. What’s more, if those were the only ontological options, Pluralism would not be a viable option. But…
With these terminological clarifications at hand, it is clear that something can indeed intertwine the physical (in the broad, everyday sense), the mental (in the neo-Kantian sense), and the abstract (as in “abstractish”). Indeed, our world is replete with such hybrid objects: psycho-cultural kinds (e.g., dining room tables, footwear, bon fires, people, sport fishing, Caribbean cruises, lasagna, the gel pen, eye make-up, ginger ale, champagne, civic unrest, colour television, punk rock, pornography, incest); intellectual artifacts (college diplomas, drivers’ licences, the Canadian dollar, the heliocentric theory of our solar system, abstract expressionism, Angry Birds, Microsoft Office); and institutions (MIT’s Department of Linguistics and Philosophy, Disneyworld, ethnomusicology, the IBM corporation, Hinduism and Christianity, the NBA, NAFTA). What my Pluralism holds, with respect to the metaphysics of linguistics, is that natural languages and their elements are metaphysical hybrids in the same sense in which the very many items above are. The word ‘dog’, e.g., is an abstractish thing, constituted by physical, mental and social relations; so is ‘the dog ran’, each of its linguistic features, and the rules that build it from the latter; similarly for English, the language to which ‘dog’ and ‘the dog ran’ belong.
Well, but can there be a science of such ordinary, hybrid objects? That’s a topic for another post.