Discussion Paper




One of the most intractable issues in the philosophy of mind is the mind-body problem. While there are substantive disagreements at issue, more frustrating is the sense that naturalist philosophers of mind are talking past one another.  The crux of the misunderstanding seems to hinge on the statement “consciousness is a brain process,” and the main culprit is the inherent ambiguity in the word “is.”  This paper utilizes George Santayana’s essay “Some Meanings of the Word ‘Is’” to make sense out of this miscommunication by analyzing what it could mean to say that consciousness is a brain process.  By considering what the word “is” may indicate, Santayana offers a non-reductive position on the relationship of consciousness to matter that can nonetheless incorporate the materialism that is at stake for the reductionist.  Consciousness is located inextricably within natural events and yet, in its essence, is never fully reducible to physical existence.


 SEQ CHAPTER \h \r 1It Depends What the Meaning of ‘Is’ Is:

Santayana, Identity Theory, and the Mind-Body Problem




            One of the most intractable issues in the philosophy of mind is the mind-body problem.  Even naturalists–who accept the fact of an organic connection between consciousness and brain activity–cannot seem to come to an agreement over how best to describe that relationship.  While there are some substantive disagreements at issue, the more frustrating aspect of these discussions is the sense that naturalist philosophers of mind are talking past one another.  Both believe, in some sense, that our mental experiences should be aligned with material events in the brain, but they differ over what it means to say that “consciousness is a brain process.”  The crux of the misunderstanding between reductive and non-reductive materialists seems to hinge on this very statement, and the difference in interpretation leads non-reductive naturalists to deny its truth and reductionists to assert that anyone who fails to affirm it is either a closet supernaturalist or unclear about what (s)he means.

            The position I am taking here is that the main culprit in the confusion between naturalist camps is the word “is.”  This little word seems straightforward enough, but the possibilities for equivocation are many.  The best way to disentangle the confusion, then, is to disambiguate the ways in which the term may be used by philosophers of mind in their arguments.  And when I think of a rich account of the possible connotations of the verb “to be,” no work seems more appropriate than George Santayana’s essay “Some Meanings of the Word ‘Is’.”  The variety of connotations that Santayana provides here are an ideal tool kit for making sense out of, if not settling, the trenchant disagreements over the reducibility of mind to matter.  By considering the different relationships that the word “is” may indicate, Santayana offers a non-reductive position on the relationship of consciousness to matter that can nonetheless incorporate the materialism that is at stake for the reductionist.  Consciousness is located inextricably within the stream of natural events and yet, in its essence, is never fully reducible to physical existence.


Identity Theory

            There are many strains of reductive philosophy of mind in which conscious experience is in some way equated with publicly observable physical events–behaviorism and functionalism, for example–and the arguments I am going to make here will apply in some form to those as well.  Identity theory is ideal for my purposes, however, because it specifically claims that a mental state is a brain state.  Consciousness and brain processes are not correlative but identical; they are one and the same thing.  This may seem counterintuitive at first, for nothing seems more unlike our qualitative experiences than electrical and chemical exchanges taking place within some lumpy grey matter.  But many things are not as they seem, and identity theorists assert that, appearances to the contrary, mental states really are just brain states. 

            Modern identity theory originates with U.T. Place (Chalmers 2002, 4), who, in “Is Consciousness a Brain Process?” makes an empirical, rather than logical, claim for the identity of mind and brain.  In doing so, he distinguishes two different notions of the word “is,” one of definition, the other of composition, and asserts that mind-brain identity is an instance of the latter.  This is a far cry from the seven connotations of “is” that Santayana provides,[1] but Place’s distinction is clarifying, nonetheless.  Place specifically denies that statements about what experience is like are translatable into statements about brain activity (Place 1956, 44-5).  Rather, when he claims that mental states are brain states, he means that they are, in a sense, made up of, or composed of, brain behavior.  Just as water may be, to our senses, sweet tasting and clear, or blue-green and flecked with sunlight, scientifically, we know that water is really nothing but a compound of hydrogen and oxygen molecules.  “Composition,” then, indicates the material substance of any given phenomenon, and it seems reasonable to claim that the physical stuff of consciousness can be nothing other than electrical and chemical discharges in the brain.  After all, neuroscience has taught us that very specific areas of the brain are responsible for equally specific aspects of our qualitative states: where those areas are damaged or lacking, our experience is as well.  If we are looking for where to locate the stuff responsible for consciousness, brains seem to be a pretty good bet.

            Place’s means of justifying the reduction of consciousness to brain processes–and this will be important later in reference to Santayana–is to distinguish between two kinds of observations, those based on everyday perceptual awareness and those made from scientific experiment.  Place notes that “two sets of observations [are] observations of the same event” when the scientific account provides an “immediate explanation of the observations made by the man in the street” (48).  In other words, when the scientist is able to provide a theoretical account of a perceptual experience, the two may be said to be identical.  When seeing a red object is explained as the reflection of light waves of certain frequencies onto the rods and cones in the retina of the eye, we mean that this is exactly what is happening when we see red.  There are not two experiences, located in space and time, that we correlate; one simply is the explanation for the other.

            There are limitations to Place’s analogy between scientific explanations of perceptions and scientific accounts of consciousness, however, for it is doubtful whether consciousness is an everyday perception of the brain.  It is not our brains that we are perceiving when we are conscious, but our general environment.  Even the metaphor of the “inner eye,” or inner sense, is problematic, for what sense organ is it that would supposedly be sensing the brain itself?[2]  Place’s colleague, J.J.C. Smart, also questions the confidence with which Place makes mind-brain identity a straightforwardly empirical matter, and asserts that, in deciding between reductionism and an epiphenomenalist dualism, no empirical test can provide a solution (Smart 1959, 155).  However, this does not lead Smart to reject identity theory; instead, he chooses to strengthen it.  Because no scientific experiment can solve the problem, nor can a logical proof demand that we accept dualism, Occam’s razor charges us to explain the phenomena as simply as possible, and adding subjective states to brain states simply provides a more complex description where a simple one will do (142).  We should not think of psychological states as composed of brain states because, physically speaking, there is nothing other than brain states that exist.  In short, there is no “irreducibly psychical” something that is being correlated with brain states. Smart notes that “[y]ou cannot correlate something with itself.  You correlate footprints with burglars, but not Bill Sikes the burglar with Bill Sikes the burglar” (142).  From this analogy, it is evident that Smart intends, as does Place, to deny that there are two natural entities that are being associated with one another.  Footprints are located somewhere, and we may infer that a human being, now located elsewhere, made them.  But subjective states are not “tracks” left by the brain.  We cannot separate them in any physical sense; therefore they are one and the same thing. 


Santayana’s Analysis of “Is”–Identity Versus Synthesis

            The example of Bill Sikes is a particularly helpful means of transition to Santayana’s “deconstruction,” so to speak, of the various meanings of the word “is” and the significance of these connotations to the mind-body problem.  Recall that Smart denies we can correlate Bill Sikes with himself because he is simply identical to himself.  Generally speaking, this appears obvious, but on closer examination it becomes evident that this statement is true in one sense, but false in another, and Smart may be unintentionally guilty of an equivocation here.

            In “Some Meanings Of The Word ‘Is’,” Santayana distinguishes seven different connotations of the verb, four of which might roughly fall under Hume’s category of relations of ideas and three under matters of fact.[3]  The first he reserves for only the strictest sense of identity and labels it, aptly enough, “identity.”  All that may be truly identical is an essence–a distinct quality or character–with itself.  The minute we try to suggest that one essence is really another, or indicates or explains some natural event, we have already moved beyond identity and are performing what Kant would call a synthetic operation.  Santayana would agree with Smart that “Bill Sikes” and “Bill Sikes” are identical, but only in the sense that the essence thus invoked is itself and no other.  The moment we claim that “Bill Sikes is a criminal in Dickens’s novel Oliver Twist,” we have combined several essences together, and thus “definition” (Santayana’s third meaning of “is”) is already something very different from identity.

            What Smart appears to mean when he claims that Bill Sikes cannot be correlated with himself is that there are not two physical beings in question, but one, were he to exist.  But what if we take a slightly more complicated fictional character (and again, imagine he is of flesh and blood existence)?  Clark Kent and Superman would be the same material entity, the one being the alter ego of the other, but can we really say that these two very different characters are identical to each other?  True, when one is around, the other is nowhere to be seen, indicating that there is only one physical object to which we are referring, but is meek and mild Clark the same personality, to say nothing of the same formal essence, as the Man of Steel?  Clearly Lois Lane did not think so.  Santayana notes that “[e]very quality possibly found in any thing, or predicated of it, is a fundamental and separate essence evoked on that occasion” (Santayana 1936, 201).  What we have in this case are two different essences–“Clark Kent” and “Superman”–being attributed (justly, I might add) to the same physical being.  It is important to note that, when we claim that Clark Kent is Superman, we are not reporting a straightforward case of identity but actually making a rather complex knowledge claim by triangulating among two essences and a physical thing.

            While, in the strict sense, only an essence may be identical with anything (and then only with itself) the first form of “is” does not get us anywhere very interesting epistemologically.  Knowledge, by contrast, requires that we move beyond identity, and while we lose the perfect adequacy of thought to thing for which traditional epistemology strives, we also gain something new by joining essences together and, by way of them, designating some material event or being.  When this occurs, each formal character, description, or explanation becomes a symbolic act of representation, and though many such symbols may refer to the same object, there is no identity between those essences or between them and the object.  In a sense, then, knowledge is an act of correlation; we need not restrict this term to connections between natural events, as Smart appears to have done.  When we predicate some essences of others (Santayana’s fourth meaning of “is”)–for example, by claiming that a Macintosh apple is red and tart–we indicate the characteristics to be correlated with each other and with the being they are supposed to represent.  And if I have never encountered this apple before, and yet I know the meanings of its predicates, will have learned something new by this synthetic act of predication.


The “Is” of Derivation and the Mind-Body Problem

            Thus far in my consideration of Santayana’s treatment of “is,” I have focused on the ways in which essences may define or predicate others, and as such, I have not yet hit on what is intended by identity theorists when they claim that consciousness is the same thing as a brain process.  Place explicitly rejects the “is” of definition, and both he and Smart deny that statements about consciousness are identical to statements about brain processes, so to this extent, Santayana’s critique of the identity of essences would not be a critique of an identity theory of mind.  However, it is dubious whether the “is” of composition is so easily equated with any of Santayana’s remaining descriptions, and this is a telling point.  Identity theory makes both an ontological and an epistemological claim: that there is one material event in question, and that one description of that event is reducible to another one.  When we claim that water is really H20, we are asserting that both terms refer to the same physical entity, and furthermore, that the latter term captures the true nature of the material object.  In extending this metaphor to consciousness, identity theory claims that consciousness and brain processes refer to the same event and that observations of brain states more fully capture its true nature (consciousness merely reporting how it “appears”).  When Place justifies this identity by referring to two kinds of observations of the same event, he is making an epistemological claim that Santayana would find problematic.  An investigation of this claim using Santayana’s concept of the “is” of derivation will make it possible to assert, on the one hand, that consciousness and brain processes amount to one natural event and yet to deny, on the other, that consciousness is “just a brain process.”

            “Derivation” is the seventh, final, and, Santayana notes, “most misleading” of all the meanings of the word “is.”  When we claim one thing is another in this way, the intention is that the first object “is derived from . . . or has the same substance” as the second (Santayana 1936, 209).  Santayana notes that, in this case, “[t]he word ‘is’ has become a synonym of ‘comes from’; it attributes to an alleged fact a source in another alleged fact, asserting that the two are continuous genetically, however different they may be in character” (210).  Truly, the assertion that one fact has a source in another could well be the “is” of composition that Place intends.  Despite the fact that consciousness and brain states have very different characteristics, they nonetheless possess the same substance.  Santayana’s example of this use of “is” involves seeing a spark and attributing it to a firefly (210).  Place, explaining the “is” of composition, asserts that a lightning flash is an electrical discharge and likens this to the mind-body relation (Place 1956, 47-8).  In all these cases, “is” is taken to indicate that a given appearance derives from a particular substance.  Ontologically, both Place’s “is” of composition and Santayana’s “is” of derivation seem quite compatible.

            However, due to the different epistemological presuppositions of the two thinkers, the similarity between composition and derivation end with Place’s insistence that brain events are the actual substance of the matter.  Santayana considers the “is” of derivation to be the most misleading because it assumes an unsupportable confidence in our ability to identify our observations with material existence itself.  For Santayana, knowledge is a transitive operation in which essences function as indirect indicators of events in nature.  In other words, all we have direct access to are intuited data, and when we make knowledge claims, we take those data to stand for something independent of our present awareness.  To return to the Clark Kent/Superman example, both names, present to intuition, truly refer to the same substantial being; but neither term adequately captures the nature of that being.  Or, to put this in Place’s language, two observations may be observations of the same event, but no observation is reducible to the other, for neither can succeed in laying bare substance itself.  As if anticipating the entire contemporary dispute over naturalist accounts of consciousness, Santayana notes:

[O]ne school of philosophers will . . . maintain that everything physical is really mental, and another school that everything mental is really physical.  A capital instance of this habit is found in the phrase . . . that something “is nothing but” something else.  . . . The phrase “nothing but” claims adequacy for the definition that follows: but a definition can define adequately an essence only, it cannot pretend to exhaust a fact . . . [Santayana 1936, 210-211].

When we are describing consciousness and brain states, one can make a strong a posteriori argument that both are, at bottom, the same natural event.  But this is something very different from claiming that one account of that event is reducible to the other.  To describe or explain a fact is to situate it within a specific disciplinary context according to a given mode of discourse.[4]  We may accept that there is one natural event–as do both the materialist and the non-reductive naturalist–but deny that one form of discourse can fully capture the issues involved with the mind-body problem.  And this, of course, is where the two schools of thought part company. 

            The appeal of reductive materialism is its reliance on scientific information.  The best accounts and predictions we have of the way matter behaves derive from the scientific method, and, perhaps as a result, much of reductionist philosophy simply equates such accounts of nature with nature itself.  But this equation forgets the complex interpretive processes involved in generating scientific knowledge and treats conclusions drawn from technically derived data as straightforward perceptions of the very core of reality.  One exception to this tendency to equate scientific fact with straightforward perception is Christopher Hill, who, in his critique of Kripke’s modal argument for dualism, indicates the problem with the notion that we might simply observe brain states:

[T]his presupposition [that it is possible for us to perceive brain processes] is highly questionable.  To be sure, we are able to use the naked eye to perceive whole brains and various parts of brains.  Further, by focussing microscopes on preparations of dead tissue, we are able to perceive certain aspects of the structure of individual brain cells.  But neither of these things count as perceiving electrochemical activity in living neurons.  Accordingly, it seems reasonable to say that brain processes lie on the theoretical side of the fuzzy line that divides theoretical entities from observable entities.  Our access to brain processes is mediated by theories.  We cannot be said to perceive them [Hill 1997, 68].[5] 

Hill’s claim that brain states cannot be directly perceived suggests a fruitful critique of Place’s reductionism, for it challenges the possibility that we are actually comparing two observations of the same event.  Recall that Place claims reduction is justified when one observation provides an immediate explanation for the other.  If anything, scientific explanations are highly mediated–by technology, processes of induction, and transactions among the scientific community.  Where Place claims to be drawing a parallel between perceptions of consciousness and perceptions of brain events, he is actually comparing introspective intuitions with complex theoretical accounts of how those intuitions are generated.  One is an appearance par excellence, the other involves abstract inferences from other appearances, in this case, technologically generated perceptions.  In neither case do we have a simple perception that absolutely captures the material event. 


The “Is” of Actuality and Non-Reductive Naturalism

            The essence of the non-reductive position on the mind-body problem is that something imperative is lost when consciousness is identified with matter.  Naturalists of this ilk do agree with materialists that there is but one natural event taking place: they share the same ontological premise, but they do not buy the epistemological conclusion.  Some, such as Thomas Nagel, point to the limitations of the objective sciences to provide an explanation of subjective life, while others, like Frank Jackson, show how knowledge of brain events cannot by themselves  yield knowledge of subjective states.[6]  These thinkers recognize that qualitative awareness is an integral part, not only of experience generally, but of our ability to know anything whatsoever.  Reductive materialists contest these positions because they assume that what cannot be treated scientifically cannot be an object of investigation.  As a result of this presupposition, they interpret the denial that consciousness is just a brain state to mean “it is not the case that consciousness is a brain state” at all.  In other words, if we deny the truth of the claim that consciousness is identical to brain states we must be asserting that consciousness is not a brain state but some other kind of natural phenomenon.  In short, reductionists confuse the denial that consciousness is identical to brain activity with the denial that consciousness is derived from brain activity. 

            Fortunately Santayana again has a meaning of “is” that can come to our rescue:  “Is, applied to spirit or to any of its modes, accordingly means is actual; in other words, exists not by virtue of inclusion in the dynamic, incessant, and infinitely divisible flux of nature, but by its intrinsic incandescence, which brings essences to light and creates the world of appearance” (Santayana 1936, 209).  Santayana uses the term “spirit” to refer to what I have been calling consciousness.  It is not itself a phenomenon but an illumination of phenomena (in other words, of qualia).  To say “he is in pain” or “I am seeing a green object” is to use “is” in this manner.  When we do so, we do not posit a second observable event correlative with the material one.  At the same time, we are indicating something true about the event in question.  To say “I am in pain” is not just a confused way of saying that C-fiber activation is appearing to me as pain.  It articulates something very different, something about the unified and total subjective state I am actually in.  If statements about conscious states indicate something actually occurring and meaningfully different from statements about brains, they should not be excluded from philosophical discussion of the mind-body problem.



            One helpful way to think of the different beliefs naturalist philosophers may hold regarding the place of consciousness in nature is provided by David Chalmers, when he divides the challenge of understanding consciousness into an easy problem and a hard problem.  The easy problem concerns questions about which mechanisms are responsible for consciousness, while the hard problem considers why such physical events should produce qualitative states at all (Chalmers 2002, 247).  Reductive materialists believe the easy problem is the only problem there is: when we have satisfied the conditions for a scientific explanation we have solved the problem of consciousness.  Non-reductive naturalists assert that there is more to be accounted for.  Why it should be the case that there is something it is like to be a kind of organism cannot be justified through science alone.  Smart claimed that Occam’s razor demands we exclude from our explanations what science cannot discover nor logic prove.  In other words, if we can’t prove the existence of subjectivity, then there can be neither truth nor falsity to the matter, and philosophy should drop the issue.  If we can explain the physical process involved without recourse to qualia, so much the worse for qualia. 

            According to the reductionist view, then, the job of the philosopher of mind is to help science figure out what consciousness is, scientifically speaking: Where is it located?  What engine makes it function?  What biological purpose does it serve?  When we have satisfied these sorts of questions, the scientistic philosopher claims we are done.  And yet, Santayana nicely articulates the significance of including consciousness in our analyses when he writes:

Intuitions are therefore not existences in the same sense of natural things, nor events after the fashion of natural events; and yet we must say of them preeminently that they exist and arise, unless we are willing to banish spirit from nature altogether and to forget, when we do so, that spirit in us is then engaged in discovering nature and in banishing spirit.  Why should philosophers wish to impoverish the world in order to describe it more curtly [Santayana 1936, 208]?

The temptation of scientism is its tidiness.  Science is very good at discovering truths about publicly observable objects, and there is nothing in principle that science cannot explain about physical existence, so why add some occult qualia to the problem when they add nothing to a physical solution?  However, by confining ourselves to what can be tested objectively, we are forced to ignore the aspect of our lives with which we are most intimately involved: our subjective experience.  Scientism shuns speculative philosophy, but with the mind we are confronted with an issue so complex that it cannot help but invite speculation.  Consciousness is a unique philosophical problem, for it is not only an object of inquiry but also the inquiring subject itself.  We philosophers are not scientists.  We can, and should, draw on scientific information where appropriate, but we are also in a position to reflect on the limitations of what science can provide and to fruitfully examine regions where it cannot tread.  Consciousness would appear to be one of those regions.




Chalmers, David. 2002. “Consciousness and Its Place in Nature,” in Philosophy of Mind: Classical and Contemporary Readings. New York: Oxford University Press.  Originally published in Blackwell Guide to the Philosophy of Mind.  Ed. By S. Stich and T. Warfield.  Malden, MA: Blackwell.

-----.  2002.  “Foundations,” in Philosophy of Mind: Classical and Contemporary Readings.  Ed. by David Chalmers.  New York: Oxford University Press.

Hill, Christopher S.  1997.  “Imaginability, Conceivability, Possibility, and the Mind-body Problem.”  Philosophical Studies  87:61-85. 

Jackson, Frank. 1982.  “Epiphenomenal Qualia.” The Philosophical Quarterly 32: 127-136.

Nagel, Thomas.  1974.  “What Is It Like To Be A Bat?”  The Philosophical Review 83: 435-50.

Place, U.T.  1956.  “Is Consciousness a Brain Process?” British Journal of Psychology  47: 44-50.

Santayana, George.  1936.  Obiter Scripta.  Ed. by Justus Buchler and Benjamin Schwartz.  New York: Charles Scribner’s Sons.

Smart, J.J. C.  1959.  “Sensations and Brain Processes.”  The Philosophical Review 68 (2): 141-156.




[1].The seven meanings of “is” are identity, equivalence, definition, predication, existence, actuality, and derivation.  I will specifically address five of them–identity, definition, predication, derivation, and actuality–in this paper.

[2].In other words, the argument falls prey to the homonculus problem, where the explanation requires another observer within consciousness to explain consciousness, and hence begs the question of what conscious observation, in fact, is.

[3].The division is not quite as clean as it sounds, for Santayana explains that our ability to combine ideas by the “is” of predication depends on empirical observation, but I separate them in this way because the first four involve comparisons of essences, while the last three make reference in some way to existence.

[4].For example, biology, chemistry, and physics all have their requisite terms, contexts, and forms of explanation, but it is debatable whether biological and chemical explanations are reducible to physical ones, as if the last explanation were the account of what is “really” going on.

[5].In this essay, Hill is actually supporting reductive materialism by critiquing Kripke’s reliance on modal intuitions to argue for mind-body dualism.  This point notwithstanding, Hill’s analysis of the difference between intuitions and scientific conclusions is significant to a critique of the epistemological, though not the ontological, claims of identity theory.

[6].Nagel’s explanatory argument is most famously expressed in his essay “What Is It Like To Be A Bat?” (1974) and Jackson’s knowledge argument appears in “Epiphenomenal Qualia,” where he presents the thought experiment of Mary, the color-blind scientist.  Both of these arguments demonstrate cases where someone possesses all the requisite scientific information and yet is still wholly ignorant of the qualitative aspects of consciousness (1982).