The obscurity of the physical : an objection to Chalmers ’ conceivability argument 1

1 I would like to thank David Chalmers, Daniel Dennett, Guido Imaguire, Patricia Marechal, Amanda Moreira, Stephen L. White as well as the anonymous referee of Filosofia Unisinos for valuable comments on previous versions of this essay whose first version dates back to the Fall of 2011, when I took a class at Tufts University with Prof. Dennett. This paper is the first out of two I wrote in aiming to follow mainstream analytic philosophy, the other one being: Moreira (2015), which I also first articulated during the years I pursued my masters’ philosophy degree by Boston College. These “Boston essays” are quite distinct from the philosophy I have practiced more recently, and which is illustrated by papers such as Moreira (2019) and Moreira (2020). 2 Lector of Philosophy at the University of Miami’s Department of Philosophy. 1252 Memorial Drive, Ashe 721, Coral Gables, 33124, FL, United States of America. Email: f.alvesmoreira@umiami.edu. ABSTRACT


Introduction
Let us start by taking three steps. First, a terminological step. P stands for all the microphysical truths of our world. P 1 stands for the microphysical truths of an individual in our world. Q stands for all phenomenal truths of our world. Q 1 stands for the phenomenal truths of an individual in our world. Q 2 and Q 3 stand for two different phenomenal truths.
My second step is an imaginative one. A zombie world is a possible world in which all the microphysical truths are identical to the truths in our world, yet no one is phenomenally conscious. This case can be put formally as follows: P & ~Q . A zombie is an individual in a possible world whose microphysical truths are identical to the microphysical truths of an individual in our world, but who has none of the phenomenal conscious experiences of the individual in our world. Formally, this case can be put as P 1 & ~Q 1 . Moreover, this case can be illustrated by the following example. When seeing the color purple, the individual in our world has what may be called a phenomenal experience: one that apparently can only be subjectively felt. The zombie, on the other hand, has no such experience. An inverted is an individual in a possible world whose microphysical truths are not only identical to the microphysical truths of an individual in our world, but who also has phenomenal conscious experiences. His phenomenal conscious experiences, however, are qualitatively different from the ones of the individual in our world. For instance, upon eating the same type of food, the individual in our world tastes raspberry (Q 2 ) while his inverted counterpart in a possible world tastes strawberry (Q 3 ). Formally put, the case of the inverted stands as P 1 & Q 3 . From now on, I will refer to the set containing a zombie world, a zombie and an inverted as the qualia trilogy, which I will technically put as P T & ~Q T . My third step is an argumentative step. Consider what may be called the straightforward conceivability argument against materialism -an argument that starts with an epistemological premise (P.1.), passes to a modal thesis (P.2.) and, then, to a metaphysical thesis (P.3.), before it arrives at its conclusion (C.) as follows: Materialism's Thesis: P T & ~Q T is not possible.
P.1. P T & ~Q T is conceivable. P.2. If P T & ~Q T is conceivable, P T &~Q T is possible. P.3. If P T & ~Q T is possible, materialism is false. C. Materialism is false. This paper's main claim is that, despite its intuitive appeal to dualists of all sorts, the qualia trilogy is merely prima facie, but not ideally conceivable. This is because current physics does not allow philosophers to est ablish a clear concept of the physical to which something else non-physical could be opposed. I emphasize that my main claim is not merely directed to the straightforward conceivability argument. Rather, my aim is to cast doubt on the first premise of Chalmers' (2010c) latest formulation of the conceivability argument. This will require more conceptual work. So, allow me to est ablish two back-up claims in the first two sections of the paper before I present what I will call the Obscurity of the Physical Objection to Chalmers' conceivability argument in the last section.

Chalmers' Conceivability Argument
The first back-up claim that I have in mind is that Chalmers' (2010c) conceivability argument is a refined version of the straightforward conceivability argument.

A. Conceivability
Chalmers' first refinement step is to claim that conceivability can be qualified in three ways. First, conceivability can be either prima facie or ideal. The prima facie conceivability is restricted to a subject's contingent cognitive limitations, whereas the ideal abstracts away from those limitations and cannot be ruled out a priori, even on ideal rational reflection. Chalmers exemplifies his point by stating that while the affirmation and the negation of Goldbach's conjecture 3 are prima facie conceivable, one of them is not ideally conceivable. For Chalmers, the three cases that form the qualia trilogy are not merely prima facie, but ideally conceivable.
Second, conceivability can be either negative or positive. Negative conceivability is what cannot be ruled out through a priori reasoning; positive conceivability is what one has the ability to form a conception. For Chalmers, the qualia trilogy could be either thought as negative or as positive conceivable. Third, conceivability can be either primary or secondary. Primary conceivability is achieved by a priori reasoning; secondary conceiv-ao de algo não físico, um mundo zumbi, um zumbi e um invertido são meramente concebíveis prima facie, mas não idealmente. Essa objeção é chamada de Objeção do Obscurantismo do Físico.
298 ability depends on a posteriori factors. For instance, "water is not H 2 O" (NotW) can be thought by a priori reasoning. Hence, it is primarily conceivable. However, NotW is not secondarily conceivable, as contemporary chemistry has a posteriori evidence that shows that "water is H 2 O" (YesW). Like NotW, the qualia trilogy is primarily conceivable in Chalmers' view. Unlike NotW, however, Chalmers claims that we do not have any empirical evidence to support the denial of the qualia trilogy.

B. Possibility
Chalmers' second refinement step is to claim that possibility can either be primary or secondary. He does so by relying on his two-dimensional notion of modality as follows.
A possible world can be viewed in two ways: as a centered world or as a counterfactual world. When a statement is verifiable as true in a centered world, it is primary possible (or 1-possible). When a statement is satisfiable as true in a counterfactual world, it is secondary possible (or 2-possible). The NotW example can help us illustrate Chalmers' position here. Imagine a possible world in which NotW is the case. On the one hand, if we take the NotW world as a centered world qualitatively identical to our world, its "primary intension" is verifiable, and the statement would be 1-possible. In other words, if the NotW world were the case (taken as a centered world), water would not be H 2 O (it would be XYZ, for example). On the other hand, a NotW world does not satisfy what Chalmers calls "the secondary intension" of NotW. This statement, then, is not 2-possible, for we know that in all possible worlds where there is water, it is H 2 O. To put it differently, if the NotW world were the case (taken as a counterfactual world), water would still have been H 2 O. Chalmers' point is that the analogy between the NotW world and the qualia trilogy case is not complete. Distinct from the former, the latter would be both 1-possible and 2-possible. This is to state not only that if the qualia trilogy (taken as a centered world) were the case, P T & ~Q T would hold, but also that if the qualia trilogy (taken as a counterfactual world) were the case, P T & ~Q T would hold. Chalmers argues that in this case the primary and secondary intensions of P T & ~Q T coincide. Something could resemble and be verifiable as water in a centered world and yet be something else not satisfiable as water in a counterfactual world. For Chalmers, nevertheless, the same does not apply to phenomenal experience. If something is verifiable as a phenomenal experience in a centered world, something is also satisfiable as a phenomenal experience in a counterfactual world. More directly, there is no pseudo phenomenal experience. "It is plausibly the case" , Chalmers states in this sense, "that anything that feels like consciousness is consciousness" (Chalmers, 2010c, p. 150).

C. A Refined Conceivability Argument
Using the distinctions discussed above, Chalmers refines the straightforward conceivability argument as follows: Materialism's Thesis: P T &~Q T is not possible.
If the above argument is valid, one has reasons to endorse Chalmers' version of property dualism, namely, naturalistic dualism. "It is naturalistic, " Chalmers tells us, "because it posits that everything is a consequence of a network of basic properties and laws, and because it is compatible with all the results of contemporary science" (Chalmers, 1996, p. 128). This view is dualistic because it entails that Q cannot be reduced and does not supervene on P. For Chalmers, this would follow from the conclusion that materialism is false. Now note that, according to Chalmers, Q cannot be reduced and does not supervene on P because "phenomenal properties seem to be intrinsic properties that are hard to fit in with the structural-dynamic charact er of physical theory" (Chalmers, 2010a, p. 133). "Arguably" , Chalmers emphasizes, such phenomenal properties "are the only intrinsic properties that we have direct knowledge of " (Chalmers, 2010a, p. 133). By a "direct knowledge" , I interpret that Chalmers means some kind of knowledge that we gain through introsp ection. Also note that Chalmers states the following: "I believe that I am conscious, that I have states with remarkable qualitative charact er available to introsp ection, that these states resist transparent reductive explanation, and so on" (Chalmers, 2010b, p. 317). Accordingly, what seems to motivate Chalmers' property dualism is the view that there is a quite obvious and explicit gap between (so to sp eak) first person knowledge acquired by means of introsp ection about phenomenal experience; and third person knowledge acquired by other means about the physical.

Objections to P.1. and Replies by Chalmers
The second back-up claim I have in mind is that Chalmers has already replied to the following two objections against the first premise of his previous (Chalmers, 1996) formulation of the conceivability argument.

A. Prima Facie, but not Ideal Conceivability Objection
This objection was suggest ed by Bailey (2007) as well as by Van Gulick (1999) and Worley (2003). However, the reasons of the former are different from the reasons of the latter two for doing so. Bailey' s point is that all conceivability arguments rely on the notion of ideal conceivability. Nevertheless, humans will Filosofi a Unisinos -Unisinos Journal of Philosophy -21(3):296-302, sep/dec 2020 The obscurity of the physical: an objection to Chalmers' conceivability argument 299 never ideally conceive. Thus, not only Chalmers' , but all conceivability arguments are unsound. Instead, the view of Van Gulick and Worley is that someday new discoveries of future physics will allow us to achieve an ideal conceivability that will show that the qualia trilogy is only prima facie conceivable.
In this sense, note that if one revises the first premise of Chalmers' conceivability argument by stating that P T & ~Q T is merely prima facie negative / positive primary conceivable, one cannot endorse the second premise's modal thesis that P T & ~Q T is possible-1 -at least not within Chalmers' conceptual framework. The matter here is that Chalmers is committed to modal rationalism, which can be taken as the conjunction of two theses: namely, (i) the modal domain can be a priori accessed from the rational domain, and (ii) x is part of the rational domain iff x is ideally conceivable. Thus, a philosopher who is committed to modal rationalism has to accept that if the qualia trilogy is not ideally conceivable, the qualia trilogy cannot be a priori linked to modality. If the qualia trilogy cannot be linked to modality, the second premise of Chalmers' conceivability argument does not follow. Without its second premise, Chalmers' conceivability argument fails to est ablish any metaphysical conclusion against materialism.
Chalmers replies to Bailey's objection by stating that there is no reason to accept that humans cannot ideally conceive. For example, it is ideally conceivable that someone exists and not ideally conceivable that 0 = 1. Moreover, he argues against Van Gulick and Worley as follows. The claim that a future ideal reflection will show that the qualia trilogy is merely prima facie conceivable requires a revision on the following approach toward the relation between physical concepts and phenomenal concepts: physical concepts are all structural-dynamical in charact er, whereas phenomenal concepts are all intrinsic in charact er 4 . There are only two ways to revise this view. First, one can embrace eliminativism or analytic functionalism: resp ectively, the view that denies the existence of phenomenal experience; and the view that argues that such experience is not intrinsic, but, rather, a relational set of functional states in a cognitive system that lead to certain behaviors. However, these positions appear to deny the manifest without providing compelling arguments to do so 5 . Second, one can follow Stoljar and expand our conception of the physical by assuming that there are also intrinsic physical properties. For Chalmers, this position also faces trouble. Stoljar (2001) formulates a distinct objection. His view is that there are two types of physical properties. On the one hand, there are theory-based physical properties (t-physical properties),

B. Expanding the Conception of the Physical Objection
properties that physical theory tells us about, or properties that metaphysically (or logically) supervene on the properties physical theory tells us about. On the other hand, there are object-based physical properties (o-physical properties), properties that physical theory does not tell us about: namely, intrinsic properties of paradigmatic physical objects and their constituents, or properties that metaphysically (or logically) supervene on these intrinsic properties. In Stoljar' s view, P T & ~Q T appears to be conceivable because Chalmers mistakenly assumes that there are only truths regarding t-physical properties within P. However, there are also truths regarding o-physical properties within P. Thus, the three cases of the qualia trilogy could not be formally put as P & ~Q , P 1 & ~Q 1 and P 1 & Q 3 in Stoljar' s view. Rather, a zombie world and a zombie would lack o-physical properties which would make them resp ectively physically distinct from our world and from any conscious individual in it. Furthermore, an individual in our world and his inverted counterpart in a possible world would have different o-physical properties. They would, then, be physically different from one another.
Chalmers responds to Stoljar's objection by claiming that his view does not exactly count as an objection because it entails Russellian monism -a view which, in Chalmers' words, "is certainly not ruled out by the conceivability argument" (Chalmers, 2010c, p. 152). Russellian monism stands for the thesis that what Stoljar calls o-physical properties are properties that cannot be revealed to us either by perception (which only reveals their effects) or by science (which reveals only their relations). Depending on the version of Russellian monism, these properties can be taken either as phenomenal or as protophenomenal physical properties, that is, properties that may (as it is the case with humans) or may not (as it is the case with chairs) give rise to phenomenal experiences. Chalmers also emphasizes that the burden of proving that Russellian monism is a plausible view would fall on the objector's shoulders. For no one has yet developed this view in detail and it is not yet clear if such a task can be accomplished.

The Obscurity of the Physical Objection
My own objection to the first premise of Chalmers' conceivability argument is also that the qualia trilogy is merely prima facie, but not ideally conceivable. However, my reason for taking such a stand is that current physics does not allow philosophers to est ablish a clear concept of the physical to which one could oppose something else non-physical -say, Q , Q 1 , etc. I call this objection the Obscurity of the Physical Objection. I claim that this objection significantly differentiates itself from the above objections. In what follows, I would like to justify such a claim by rethinking the objections presented in the last section.

A. Rethinking the Prima Facie, but not Ideal Conceivability Objection I: Bailey's View
As far as I am concerned, Chalmers may be right in claiming that Bailey's paper fails to make a convincing case for the thesis that humans will never ideally conceive anything whatsoever. However, it is important to emphasize that one does not have to be committed to the view that there is no ideal conceivability to cast doubt on the first premise of Chalmers' conceivability argument. Instead, all it takes to rule out such a premise is the considerably weaker thesis that the qualia trilogy is not ideally conceivable. Most importantly, note that Chalmers does not take into account two important concluding remarks made by Bailey. The remarks I am thinking are the following ones. Remark 1: "Chalmers presupposes that we have adequately complete knowledge of the microphysical subvenients for conscious experience" (Bailey, 2007, p. 13). Remark 2: "there is currently no reason at all to think our knowledge of the physics of consciousness is complete" (Bailey, 2007, p. 13). My view is that, even though Bailey's objection does not follow, his concluding remarks do. In this sense, consider that the notion of "conception of nature" is in the core of Chalmers' formulation of the mind / body problem. The matter is that one can argue that Q "fits uneasily into our conception of the natural world" (Chalmers, 2010a, p. 103) iff one assumes that we hold a complete conception of P. More directly, in order to oppose P to something else, it is necessary to know what P is. Chalmers assumes that we currently have this knowledge when he claims that all members of P are structural-dynamical, whereas all members of Q have an intrinsic charact er. In doing so, he repeats a Cartesian move within a 21 st century scientific context that does not seem to allow it. Let me justify this last point with the help of some historical background given by Chomsky (1993).
In the 17 th century, Descartes took "thinking" (res cogitans) as the mind's only essential property. Further, he defended the thesis that for every x, such that x is a member of P, x has "extension" (res extensa) as its single essential property. Thus, Descartes held a precise concept of the physical by means of which he could endorse the following conceivability claim. As "extension" (res extensa) ≠ "thinking" (res cogitans), one can have a clear and distinct idea of the body and the soul as distinct substances. Chalmers' point is quite similar: namely, that, as "structural-dynamical" ≠ "intrinsic" , the qualia trilogy is ideally conceivable. The problem is that Newton ruled out the Cartesian restricted and precise conception of the physical when he postulated the existence of non-extended forces. Ever since, we are left with concepts of "physical" or "material" that resist to precise definition. In this sense, take into consideration the following passage by Chomsky:

Ninety percent of the matter of the universe," physicists tell us, "is what is now called dark matter -dark because we don't see it; dark because we don't know what it is," indeed, "we do not have the slight-
est idea of what 90 percent of the world is made of." (Weisskopf 1989) Suppose the dark matter turns out to be crucially different from the 10 per cent of the world about which there are some ideas. The possibility cannot be discounted in principle; stranger things have been accepted in modern science. Nor can it be excluded in the case of theories of mind (Chomsky, 1993, p. 85). This is to say that the question "what is the physical?" remains open for contemporary physicists 6 , and does not allow a philosopher to complete the following formula. For every x, such that x is physical, x is___________. Chalmers, on the other hand, problematically completes such a formula in pointing toward a quite simplified view of contemporary physics. Chalmers does so by relying on a different (regarding Descartes) but still considerably simple answer to the question "what is the physical?": the answer that the physical is structural-dynamical in charact er. This answer makes it considerably easy for Chalmers to prove property dualism. This is because, as Montero (2009) underlines, "if one […] thinks that the mental has some sort of non-structural nature [as Chalmers does] and also that there is a sharp divide between the non-structural and the structural [as Chalmers also does], it is easy to be led to the view that the mental is not physical [as Chalmers is]" (Montero, 2009, p. 183). Against Descartes, Spinoza claimed in the 17th century that no "one has hitherto laid down the limits to the powers of the body. " 7 In the 21st century, one can still repeat Spinoza's claim against Chalmers by insisting that one cannot assume that our current knowledge of the physical is complete.
Indeed, the very notion of the "physical" seems quite obscure. Given this factor, I do not think that one can ideally conceive a distinction between the physical and the phenomenal, as Chalmers claims. As stated above, I take that Chalmers is motivated by the fact that we have some sort of "first person" knowledge acquired by means of introsp ection about phenomenal experience, and a third person knowledge acquired by other means about the physical. As far as I am concerned, this might be the case. However, given the obscurity of the notion of the "physical" , such fact is not enough to back up the claim that P T & ~Q T is ideally conceivable. Rather, this only indicates that P T & ~Q T is prima facie conceivable. More directly, P T & ~Q T is merely conceivable for those, like Chalmers, who have the problematic dualistic intuition that consciousness resists any kind of third person approach. This intuition, though, is not enough to back up the thesis that P T 301 & ~Q T is ideally conceivable. This is because physicalists of all sorts have a contrasting, but likewise problematic intuition: namely, that, to put it in Smart's terms, "everything should be explicable in terms of physics […] except the occurrence of sensations [or phenomenal experiences] seems […] to be frankly unbelievable" (Smart, 1959, p. 142).

B. Rethinking the Prima Facie, but not Ideal Conceivability Objection II: Van Gulick's and Worley's View
Let me start to differentiate my objection from the views of Van Gulick and Worley by considering the following passage by Chalmers: "[1] physics and physical concepts are all structural-dynamical in charact er (and [2] new scientific developments are unlikely to change this)" (Chalmers, 2010c, p. 155, my emphasis). Now let me emphasize that I claim that the qualia trilogy is not ideally conceivable today. My view is that [1] is a highly problematic assumption that we have current reasons to resist. I am not merely claiming that future physics will someday show that the qualia trilogy is not ideally conceivable. This is the view of Van Gulick and Worley who cast doubt on [2] of the above passage. I think that the problem with their stand is that one cannot rely on a future theory to rule out a current one. Otherwise, one would be able to rule out all current theories whatsoever by relying on the following type of argument. P.1. Current theory A argues for thesis A. P.2. Future theory B will show that thesis A does not hold. C.1. Thus, thesis A does not hold. It seems, however, that C.1. does not follow from P.1. and P.2. Rather, these premises only est ablish C.2: the view that thesis A will not hold in the future. The problem is that C.2. is a considerable weak (perhaps even trivial) conclusion because it is plausible to think that the majority (if not all) of our current empirical theories will not hold in the future -esp ecially if one thinks about a distant future, say, one million years from now 8 . Van Gulick and Worley merely est ablish a conclusion quite similar to C.2.: that the qualia trilogy will be ruled out by ideal reflection in the future. My view is that this conclusion seems to be almost trivially true, as the majority (if not all) current philosophical arguments may not hold in a distant future.
I agree with certain points made by Van Gulick and Worley, though. First, because I fail to see Chalmers' reasons for assuming that future-physics is unlikely to change. It is obviously more likely that future-physics -from a thousand, a million years from now, etc -will be drastically different from our current physics. Second, because I do not think that the one who claims that the qualia trilogy will be ruled out by future ideal reflection has to revise the dichotomy between physical concepts (structural dynamical) and phenomenal concepts (intrinsic) by assuming eliminativism, analytic functionalism or Russellian monism -three positions that are more problematic than property dualism, at least in Chalmers' view. Instead, it seems that future-physics will allow one to conceive the relation between physical and phenomenal concepts in new terms still not present in our current debate. The history of physics gives us reason to think like this. For example, the physics of Newton and Einstein did not only prove that Descartes' thesis that extension is a necessary property of every physical thing was wrong, they also dealt with the physical within a new conceptual framework inconceivable from a Cartesian point of view.
Third, because I also take that the qualia trilogy is still prima facie conceivable. My point is that despite its (to use Putnam's (1987) expression) lack of "clout" from current physics, the qualia trilogy is conceivable on an intuitive level. The problem (as stated earlier in sub-section A of second section) is that the second premise of Chalmers' conceivability argument only follows if the qualia trilogy is ideally conceivable -at least as far as Chalmers remains committed to modal rationalism. 9 Chalmers could still make a case for the second premise of his conceivability argument if he endorsed a position that may be called modal pluralism. I call modal pluralism after the conjunction of two theses: namely, (i) the modal domain can be a priori accessed from the rational domain, and (ii) the members of the rational domain can only be vaguely determined so that only upfront contradictions (of the form Q and ~Q ) are excluded. The problem is that it is quite debatable if modal pluralism can be assumed. Note that one consequence that may follow from such a view is that all conceivability arguments are, arguably, trivial. Chalmers evidently does not want to embrace such a conclusion. For if every conceivable scenario that does not evolve an upfront contradiction were possible, it would be hard to justify why one ought to take the qualia trilogy seriously. Most importantly, nothing in Chalmers' works suggests that he would endorse modal pluralism. I take, then, that if one revises the first premise of Chalmers' conceivability argument by claiming that the qualia trilogy is merely prima facie, the second premise does not follow and the argument fails.

C. Rethinking the Expanding the Conception of the Physical Objection: Stoljar's View
As far as I am concerned, Chalmers' reply to Stoljar' s objection may hold. Indeed, I fail to see the significant difference (regarding Chalmers' property dualism) of assuming o-properties and embracing Russellian monism. The matter is that Stoljar' s move seems merely to replace one somehow intuitive dualism for another non-intuitive dualism: a (so to sp eak) "property dualist" dualism on phenomenal properties and physical properties for a (so to say) "Russellian monist" dualism on t-physical prop-302 erties and o-physical properties. Moreover, Stoljar does not seem to present strong reasons for postulating o-physical properties without relying on physics to do so. Note, however, that if physics does not have authority over the physical, it is hard to understand which discipline has (or ought to have) such an authority.
Most importantly, let me differentiate my view from Stoljar' s as follows. A supporter of the Expanding the Conception of the Physical Objection is basically stating that one ought to say more about the physical. In other words, Chalmers should not only claim that physics has t-physical properties, but also that the physics has o-physical properties. Note, then, that Stoljar' s objection is not motivated by the belief on a future expansion of physics. Rather, what motivates him is a representation of current physics distinct from Chalmers' . On the other hand, a supporter of the Obscurity of the Physical Objection is basically stating (on a more skeptical vein) that one ought to say less about the physical. This means that Chalmers should not have claimed to know what t-physical properties are. Moreover, as he should not have presupposed that he knows exactly what P or P 1 are, he should not have opposed them to Q , Q 1 Q 2 or Q 3 and claimed that the qualia trilogy stands for cases physically identical to our world or to the individuals in it. Like Stoljar' s objection, then, my objection is not motivated by the belief on a future expansion of physics. Like Stoljar, what motivates me is a representation of current physics distinct from Chalmers' . Nonetheless, my representation of current physics, I believe, is less problematic than Stoljar' s. This is because I do not commit myself to the distinction between t-physical properties and o-physical properties. Rather, I merely claim that contemporary physics does not allow philosophers to postulate a precise notion of the physical. Furthermore, the Obscurity of the Physical Objection does not entail Russellian monism. Instead, from the premise that current physics does not provide a precise concept of the physical, three conclusions follow: 1. that the mind / body problem cannot be formulated (Chomsky, 1993); 2. that the mind / body problem should be formulated in new terms which do not use the notion of the physical (Montero, 2009); or 3. that the physical is a mystery (McGinn, 2011). Unfortunately, I do not have the space to compare these three views or to develop a fourth alternative here. However, my belief is that these approaches are significantly different from Chalmers' stand on the mind / body problem. Thus, different from the Expanding the Conception of the Physical Objection, the Obscurity of the Physical Objection counts as an objection.

Conclusion
I conclude that the Obscurity of the Physical Objection calls for a new reply by Chalmers. For (as the paper's third section shall have showed) it poses a different challenge to the first premise of Chalmers' conceivability argument; a challenge that cannot be identified with those raised by the Prima Facie, but not Ideal Conceivability Objection or the Expanding the Conception of the Physical Objection presented in this paper's second section.