The mental realm
I’ve treated the existence of the first realm, that of physical entities, as self-evident. The existence of a mental world is even more compelling.
The nature of the physical world surrounding us is subject to constant skeptical challenges, like Zhuangzi’s account of his dealings with Morpheus: "I do not know whether I am a man who dreamt he was a butterfly, or whether I am now a butterfly dreaming I am a man." Zhuangzi may be unable to tell dream from physical reality. But his experience of being a man is irrefutable.
Of course that is only irrefutable from Zhuangzi’s perspective; I cannot truly know what he experienced. I can only speak for myself, as can you. Right now, I am experiencing bodily sensations, sensory perceptions and a stream of thought, accompanied by an inner monologue, as I’m composing this prose.
Such experiences are commonly associated with the mind, and, in more technical terms, filed under the category of mental states. Where do we go from there? It appears we are facing two fundamental questions: (1) Are we justified in speaking of a mental world as distinct from the physical universe?, and (2) What characteristics are common to the motley crew of mental states we’ve evoked, and are we justified in lumping them all together under the singular concept of mind?
The mental and the physical
Humans, across cultures and eras, have been prone to contrast the physical and mental domains. That results from a tendency to spontaneously treat the content of mental states as an object. Let’s say I close my eyes and think about the color green. The object "green mental image" is of a peculiar character: (1) it evidently shares a property ("being green") with sensory perceptions, although there is nothing physical in my field of vision that is green (my eyes are closed), nor is there anything green inside my head; (2) it is private — as far as I know, nobody can tell that I’m imagining green; (3) it is subjective — if you imagine green and I imagine green, there is no way to compare what we’re seeing; (4) it is qualitative — I cannot make any measurement on it. All in all, it seems fairly natural to set aside mental states, whatever they may be, from physical objects.
These discrepancies justify our talking about physical and mental phenomena as distinct, but this does not carry any metaphysical significance. After all we do speak of living beings and of minerals in starkly different terms, and they differ with regards to major properties, but no one talks of a "vital realm" as distinct or juxtaposed with the physical universe. That is because vitalism lost the argument against mechanism and we know all life-related phenomena to be reducible to physical ones. Not only is this argument not settled as to matters of the mind, it is as debated as it ever was: Buddhists believe mind and matter are different aspects of a single stuff; Epicurus thought the soul was made of the same atoms as matter; Aristotle saw the soul as the form of the body (in the same way as form makes a Venus-shaped piece of clay into a statue); Descartes argued the mind and matter were two separate substances altogether... All those positions, and more, persist in a modern form to our day. We will delve into the main ones in a later section, when I’ll consider the different relationships the hypothetical three realms may entertain.
Particularly consequential in such reflections is the mind-body problem. We all know that physical and mental phenomena are intertwined: things that I have seen with my eyes (a physical organ) exists as images or memories I can conjure "in my mind"; conversely, the thought that I ought to move my arm actually makes it move — that’s mental causation. One may believe that the physical and mental worlds are independent, that one supervenes on the other, or that one is reducible to the other, but the issue of how their denizens interact remains an open question.
The marks of the mental
From a common-sense inventory of mental states we’ve been able to compare and contrast those with physical entities. Now comes the harder task: to describe more precisely what exactly "mental" entails, that is, to search for the mark of the mental.
Once again, this issue is orthogonal to metaphysical ones like the mind-body problem. Even from a staunch physicalist standpoint, whereby everything mental is reducible to physical processes, there is conceptual tension between the mental and the rest, which needs to be examined and decomposed to its quintessential elements in order to make progress.
There are two candidates for our marks of the mental: phenomenality and intentionality.
a mental state is phenomenal when subjects are having an experience, or when "there’s something it’s like" to be in that state. When I hear a sound, feel pain or picture a blue sky, my state of mind has a felt, qualitative, experiential aspect. It makes sense to talk about what it’s like for me.
the intentional nature of a mental state is apparent when it is about, or directed at something. My belief that Schubert is a great composer, my desire for a mandarine, my fear that Federer could retire, fit in that category.
In this dichotomy we hear echoes from a persistent contrast throughout the history of philosophy between sensations and thought. Those seem indeed to be archetypes for our two categories: aches, pleasure and other bodily sensations are indisputably phenomenal states; thoughts, beliefs, fears, wants are exemplarily intentional. Sensory-perceptual states, however, appear prima facie to have both phenomenal and intentional aspects.
As we shall see shortly, how we conceive of the relationship between phenomenality and intentionality is key to our apprehension of a unified mental realm.
Phenomenal states
What it’s like:
I’ve mentioned sensory perceptions and bodily sensations as typical phenomenal states. We have an enormous amount of knowledge about human sensory organs, our nervous system, and of course the brain. Now picture a future where we would know everything about perceptual states from a biological perspective, down to the behavior of individual neurons and the exact concentration of neurotransmitters. Would this constitute a complete understanding of perception? That is the implicit question in all discourse about phenomenality: is there a phenomenal residue that is irreducible to physical explanation? Starting with Thomas Nagel, this residue has often been described in terms of "what it’s like". Nagel aimed to capture the qualitative, first-person notion of being a conscious organism, that which makes questions about the mind truly intractable, taking the examples of a bat. Bats are mammals — if one accepts that some animals at least are minded beings, bats would be included for sure. However, out of all mammals they might be the one with the furthest sensory apparatus from ours. Bats use echo-location to perceive their surroundings, a sense that is well understood from an objective, scientific, perspective. Nagel asks us, is there something else in the world that "nature’s blueprint" to make bat, is there a subjective experience of "what it’s like to be a bat" that no one but a bat could ever know?
Earlier on, Frank Jackson had crafter the famous thought experiment of Mary’s room: Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like "red", "blue", and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence "The sky is blue". ... What will happen when Mary is released from her black and white room and sees the blue sky? Will she learn anything or not?
In other words: phenomenal experience, which is what Mary may have, is how you perceive with your senses, how your feelings feel to you, etc. This criterion is a pretty good fit for our intuitive sense of what should mark the mental. Most people would agree, there is nothing it’s like to be a leaf falling from a branch, nothing it’s like to be a computer opening a webpage. But none of this (nothing in this section, really) is even close to a consensus: some philosophers would say the leaf and the computer are subjects, others that Mary learned nothing coming out of the room and that there is no phenomenal residue, and so on.
Qualia:
more precisely, we know there is not merely "something it’s like" to have a phenomenal experience, but rather some particular thing, or things. In my experience of trying a new Merlot, visual, olfactory and gustatory perceptions, as well as mood and emotion, will coincide. The overall impression depends on the interaction between them, but it also seems I can conceive of them separately.
Qualia are hypothetical properties of phenomenal mental states that are typically seen as monadic features of experience; sometimes they’re referred to as "raw feels". Both the definition and the mere existence of qualia are heavily disputed topics in contemporary philosophy of mind, so remember we shall tread lightly and avoid the slightest whiff of certainty. I’ll mention some aspects of qualia that are at least "traditional" and fairly common. First, qualia are ineffable: I can tell you what I’m thinking or what I desire; I can tell you the color of these flowers is halfway between poppy and daffodils, and I can tell that blood is red; but I cannot tell what it’s like, absolutely, to see red. On a related note, qualia are intrinsic properties of phenomenal objects: they don’t depend on relations with other mental states — for instance, the emotion I feel drinking wine may depend on the relation between its taste, my memories and my mood; but the "raw taste", the gustatory quale is not in any such relation. Many also see qualia as incorrigible in the sense they cannot be "wrong" since they are immediately accessible in consciousness, without intermediary — my belief that I’m seeing a physical pink crocodile can be wrong, because I’m dreaming or hallucinating, by the raw feeling from that pink color cannot be "wrong" in the same sense; it is what it is. Lastly, qualia is often thought to be nonrepresentational, or to have no intentional content; this would mean a quale is "not about anything". When I see a red apple I’m in a phenomenal mental state that has intentional content: the red apple. But the raw visual feeling of seeing red is not directed towards the apple: it just is.
Phenomenal organization:
"qualia" and "phenomenal properties" are sometimes used interchangeably nowadays, but they shouldn’t be conflated. Qualia, if they exist, are what makes phenomenality special, but phenomenal organization, the kind of order and structure found within the domain of experience, goes beyond simple raw feels. Actually, Kant, Husserl and countless phenomenologists have observed that the phenomenal structure of experience is is richly intentional and involves complex representations of self, body, world, space, time and more conceptual forms.
It appears, then, that most of our "typically phenomenal" states like perception or sensation are inextricable from intentional content. Qualia, then, may be useful as an explanatory device, or may even be experienced alone in certain states of consciousness, but in daily life they are part of a more complex structure of mental aspects. My happy mood is a phenomenally raw feeling, but it is concretely inseparable from a set of representations about myself.
There are debates about how to deal with this term structure. Some have argued for a so called "thin" view of phenomenality whereby phenomenal properties are strictly limited to juxtapositions of qualia. In that sense, all of the representational content we have evoked would not be connected to a "phenomenal state". The rationale is that there is no distinctive experience in believing that 6 is a perfect number or that I like the Beatles; these can be incidental to a phenomenal experience (for instance, listening to a Beatles song), or conversely, having those thought can elicit some phenomenal feel, but there is "nothing it’s like" to have the cognitive state itself. Others hold a "thick view" that basically rejects this strict separation. The phenomenal experience of what it’s like to see a photo of John F. Kennedy would then not be limited to the spatial aspects of his face, but would be enriched by all my knowledge, beliefs and thoughts about him.
Intentional states
Intentionality is the mind’s ability to direct itself onto something. If you have hopes, beliefs or desires, then you must hope, believe or desire something; hence they shall be called intentional mental states. (It should be noted that intentionality, so construed, is not intention; having the intention to do something is indeed an intentional state, but intentionality in general is richer). We can talk equivalently of representational states, where the representation is what the mind is directed upon.
Modern interest in this concept can be traced back to this seminal quote from Brentano: "Every mental phenomenon is characterized by what the Scholastics of the Middle Ages called the intentional (or mental) inexistence of an object, and what we might call, though not wholly unambiguously, reference to a content, direction toward an object (which is not to be understood here as meaning a thing), or immanent objectivity. Every mental phenomenon includes something as object within itself, although they do not do so in the same way. In presentation, something is presented, in judgment something is affirmed or denied, in love loved, in hate hated, in desire desired, and so on. This intentional inexistence is characteristic exclusively of mental phenomena. No physical phenomenon exhibits anything like it. We can, therefore, define mental phenomena by saying that they are those phenomena which contain an object intentionally within themselves."
To unpack what that means, let’s use the three features of intentional states most frequently invoked in modern theories of intentionality:
Mode: From what precedes, it is clear that intentional states are not just arrows pointing at something. Obviously, fearing that Federer may retire, believing Federer will retire, or hoping Federer does retire, are completely different things. Each corresponding mental state has its own dispositions toward certain phenomenal experiences or action. The difference between them is said to be one of mode.
Object: We said intentional states are directed upon, or about, something — that is the intentional object. Thence lies the immediate puzzle of intentional inexistence. I can think about my wife or crave an apple from the kitchen; they are ordinary objects with a connection to the physical world around me. But I can also like dinosaurs, even though they are extremely remote in time from the concrete token of that idea (an occurrent thought in my mind, or a vocal utterance whereby I made that statement). I can also desire to have a pet phoenix, even though there is no such thing. We can see how Brentano insisted on intentionality as a mark of mental phenomena. The uncontroversial logical principle of existential generalization seems to have been broken (at least prima facie). In the non-mental world, the facts that Charon orbits around Pluto, or that a lion has chased a zebra, imply that Pluto has at least one natural satellite and that lions and zebras exist. But someone’s hope that Elvis Presley is sitting in a Tennessee diner today has no bearing on the King’s continued existence in 2021. The question of what intentional objects are is of course tremendously important; there will be ample discussions of the topic in the section relative to abstract objects.
Content is what is being thought, said, believed, desired, feared, perceived, hoped... Naively put: if I think that Ann is tall, then the object of that mental state is Ann, but its content is the proposition "Ann is tall". (It has sometimes been argued that intentional content can only be propositional, which would entail that intentions are solely expressed in terms of ’that’-clauses. It is not straightforward to accept that thesis, especially as regards perceptual states, so we will accept non-propositional intentions).
Going beyond pre-theoretical intuitions, can we say more about what content is? To do so, let us introduce Frege’s puzzle: how can one rationally hold two distinct singular beliefs about the same object? Consider Barack Obama: he is the 44th president of the United States — these two entities are identical. The 44th president is tall, was born in 1961 and likes basketball, because those things are true of Barack Obama. And yet, it is entirely possible for someone to believe that (1) Obama is a Democrat and (2) the 44th president is a Republican; only one of these propositions is true, but both can be ascribed to the same subject’s beliefs. Even better, consider these two statements: "she claims that Obama is the 44th president" and "she claims that Obama is Obama". The former is a display of historical knowledge; the latter is a triviality that just demonstrates mastery of kindergarten English. The logical principle we’ve invalidated here is the indiscernability of identicals: in an intensional context, it is not the case that \(a=b\) should entail that everything true of \(a\) is equivalently true of \(b\).
We’re landing back onto a concept encountered way back in our chapter on classification. You may remember that extensional classes are built directly from their components, whilst intensional classes are defined on the basis of a shared quality. It is then possible for two classes to share extensions but differ in the way they’re intensionally characterized.
For instance, it is now known that all animals with a heart also have a kidney, and vice versa. The concepts "creature with a heart" and "creature with a kidney" then share the same extension. But these expressions don’t have the same intensions — in semantic terms, we would say they do not mean the same thing. This is why believing that "creatures with a kidney all have a heart" and that "creatures with a heart all have a heart" are not the same things at all.
Examples abound, but Frege devised a now-classic one, that of Venus. Today, schoolchildren know Venus as the second-closest planet to the Sun. Early Romans had observed that "stars" were visible at dawn and at dusk, close to the Sun, but had not yet gathered they were actually the same object. To this day, Venus can be called "the morning star" or "the evening star". The corresponding Roman names were Phosphorus and Hesperus.
"Hesperus" and " Phosphorus" pick out the same object, Venus. Yet, as in previous examples, it does not appear to be the same to believe that "Phosphorus is Phosphorus" or that "Phosphorus is Hesperus". If the difference between Hesperus-thoughts and Phosphorus-thoughts does not lie in their object nor their mode, then it must be in "something else": mental content can play that role.
It is now visible that discussions of intentional mental states are inseparable from language. Linguistically competent subjects would say that the names "Phosphorus" and "Hesperus" may share a reference, but they don’t have the same meaning. For that reason, we can observe that mental content is actually a semantic concept. A detailed account would then take us on a long detour. I will still present three fundamental strategies which we’ll encounter time and time again.
The Fregean strategy is to accept the intensional nature of content. Gottlob Frege’s semantics associate with each proper name a reference (Bedeutung) and a sense (Sinn). The reference of "Hesperus" is the planet Venus, and its sense is a mode of presentation of that object, whose connotation is roughly that of "evening star". Senses are individuated in terms of cognitive significance. It is a priori to a rational subject that Hesperus is Hesperus, but not that Hesperus is Phosphorus, hence the discrepancy in senses.
Similarly, thoughts about Hesperus have Venus as an object, but the sense of Hesperus as a content. The content of mental states involving complex propositions are functions of their components’ senses, not of objects. Senses then act as an intensional screen between mental content and the outside world, though Frege considers them as a sui generis category and doesn’t shed light on their nature.
The Russellian strategy retrieves extensionality by way of structure. Bertrand Russell did not think that mental content involved intensional meanings like Fregean sense. He believed that objects we are directly acquainted with have no meaning beyond what they refer too. However Russell was very stringent as to what that encompassed. An object right in front of me, or an old friend, may qualify. But Russell had it that other singular terms, even proper names, were in fact abbreviated descriptions.
Then thoughts about Hesperus would truly be about "the celestial body that can be observed close to the sun, at dusk". With that in mind, "Hesperus is Phosphorus" is not an identity relation between two co-extensive objects, it is an existence statement: "there is a thing \(x\) which (1) is a celestial body that can be observed close to the sun, at dusk and (2) is a celestial body that can be observed close to the sun, at dawn". The mental content is then not individuated via intensions but via a logical structure that binds extensional entities (objects, predicates...) together.
The Millian strategy simply denies there is more to mental content than intentional objects. Co-referring names are simply tags that we hang onto the same object. Hesperus-thoughts and Phosphorus-thoughts have the same content: they’re just thoughts about Venus. Of course, Millians cannot deny the differences in cognitive significance that we observed; they just deny that it is of any semantic import. Back in Ancient Rome, everyone believed that Phosphorus was not Hesperus, but to Millians that false belief should be ascribed to something like pragmatics or social context, not to individuals’ mental content. As we shall see later, this type of view leads to modern positions like semantic externalism.