The hard problem of consciousness by no means sprang forth fully armed from the minds of contemporary philosophers. Neither Chalmers nor Nagel is the first thinker to pose the question of how immaterial perceptions relate to material objects. Indeed, Chalmers’ formulation adopts essentially the same metaphysical underpinnings that Descartes set forth in the seventeenth century. Chalmers himself acknowledged this lineage:
Any number of thinkers in the recent and distant past…have recognized the particular difficulties of explaining consciousness and have tried to face up to them in various ways. All my paper really contributes is a catchy name, a minor reformulation of philosophically familiar points, and a specific approach to dealing with them.
“Moving forward on the Problem of Consciousness.” Journal of Consciousness Studies. 1997.
While they present a similar problem, however, the early-modern Frenchman and the post-modern Australian pursue different solutions to it. Descartes, for instance, after presenting the body as an aggregate of mechanical interactions between physical components, offered the philosophically unsatisfying solution that the pineal gland explains how the animate soul interfaces with the mechanical body. In Descartes’ estimation, this psychophysical transmutation in the conarium was sufficient to explain how physical processes of res extensa could produce psychic experiences in res cogitans—a sufficiency largely dependent on Descartes appeal to a benevolent God, who “surely did not give me the kind of faculty which would ever enable me to go wrong while using it correctly.” Several decades before, the meteoric physicist Galileo Galilei had tacitly introduced this explanatory gap between qualities and bodies which Descartes assumed, and for which the philosopher John Locke would provide the most memorable formulation as the distinction between primary and secondary qualities. In Locke’s own words from An Essay Concerning Human Understanding, first published in 1690:
The Ideas of primary Qualities of Bodies, are Resemblances of them, and their Patterns do really exist in the Bodies themselves; but the Ideas, produced in us by these Secondary Qualities, have no resemblance of them at all. There is nothing like our Ideas, existing in the Bodies themselves. They are in Bodies, we denominate from them, only a Power to produce those Sensations in us: And what is Sweet, Blue or Warm in Idea, is but the certain Bulk, Figure, and Motion of the insensible parts in the Bodies themselves, which we call so.
By “ideas,” Locke refers to what we might ordinarily call “perceptions” and what contemporary philosophers call “qualia.” This passage from Locke, therefore, represents a pivotal moment in the evolution of the hard problem of consciousness. In fact, Locke was the first thinker to employ the term “consciousness,” in its modern sense. Until Locke’s time, it had retained the same meaning of its Latin counterpart: roughly “knowing together” in the sense of conspirators. Thus Brutus and Cassius could have been said to have been “conscious” on the Ides of March in 44 B.C. and it would have meant that they shared in the knowledge of their plot to kill Caesar. In the same essay in which Locke sets forth the distinction between primary and secondary qualities, he stipulatively defines consciousness as “the perception of what passes in a man’s own mind,” and since that time, the older meaning is considered obsolete.
Locke was clearly lending his voice to the spirit of the age, and this is likely to account for his lasting influence. In respect to the theme above, Locke articulated the same distinction which Galileo had drawn in 1623 in The Assayer:
I think that tastes, odors, colors, and so on are no more than mere names so far as the object in which we locate them are concerned, and that they reside in consciousness. Hence if the living creature were removed, all these qualities would be wiped away and annihilated.
Descartes, echoing his Pisan counterpart, asserted in 1644 that:
those things which, in external objects, we call by the names of light, color, odor, taste, sound, heat, cold, and of other tactile qualities…that we are not aware of their being anything other than various arrangements of the size, figure, and motions of the parts of these objects which make it possible for our nerves to move in various ways, and to excite in our soul all the various feelings which they produce there.
While Locke continued to unfold his philosophical project in the same current as Galileo and Descartes, other philosophers attempted to supplement the Cartesian model, given the latter’s inability to provide a satisfying explanation for secondary qualities. Baruch Spinoza, for instance, posited in the latter part of the seventeenth century that, in reality, all qualities, whether primary, secondary, tertiary, or otherwise, were in reality mere modes of a single substance, to which we give the name “God.” In this manner, the explanatory gap was revealed as an illusion. George Berkeley took a rather similar approach to the hard problem in its nascent formulation when the former set forth his doctrine of esse est percepi in the first decade of the eighteenth century. In Berkeley’s conception, “to be is to be perceived,” simpliciter. The single thing that we know with the greatest certainty is our own experience. To posit a material world by which to explain this experience, therefore, Berkeley held to be an inference that lacked sufficient reason. As a faithful bishop of the Catholic Church, Berkeley had no trouble in invoking God as the guarantor of the objectivity of subjective experience. Thus, Berkeley resolved the Cartesian dilemma by doing away with res extensa, or bodies, or material objects, as they are ordinarily conceived. In place of the mechanistic material universe as most modern thinkers conceived of it, Berkeley offered an ultimate idealism. Against the Charybdis of solipsism, which is the perennial threat to any idealist philosophy, Berkeley happily responded with the Ground of Being.
Before long, however, advances in the sciences seemed to offer explanations in purely physical terms without any need to invoke a supernatural being. An iconic though perhaps apocryphal statement by the mathematician Pierre Simon Laplace epitomises this trend. As the story goes, after presenting a nebular model of celestial mechanics to Napoleon, the emperor questioned the thinker as to what was the role of God in the conception which he had so elegantly presented. “Sire, je n’ai pas eu besoin de cette hypothèse,” (“Sir, I had no need of that ‘hypothesis.’”) was Laplace’s brilliant riposte. The physicist Stephen Hawking expressed the same sentiment, though with slightly less ingenuity, in a book published just after his death in 2018. “Did God create the quantum laws that allowed the Big Bang to occur?” Hawking asked, and then continued: “I have no desire to offend anyone of faith, but I think science has a more compelling explanation than a divine creator.” In Hawking’s view, “philosophy is dead… [since philosophers] have not kept up with modern developments in science. Particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge.”* We will have to return to this point later in this exploration, but first we must perform an investigation which the eminent physicist’s quote suggests that he did not. Namely, we must explore the philosophical history of modern science thus to understand the basis of Hawking’s claim as well as the origin of the hard problem of consciousness.
In spite of Laplace’s optimism that the methods of modern science could explain the macrocosm in entirely naturalistic terms, many thinkers still assumed that the microcosm demanded recourse to a supernatural power to explain the human being. Descartes, for instance, despite proposing that res extensa could be accounted for in purely mechanistic terms, still affirmed a doctrine of the immaterial soul as the ghost in the machine which could account for “the only unquestionable fact of our experience.” Indeed Descartes appeals to just this unquestionability with his notorious phrase “cogito ergo sum.” The philosopher and polymath Gottfried Leibniz articulated the explanatory gap with utmost clarity in a passage from Monadology, written in 1714:
Furthermore, one must concede that perception, and all that depends upon it, are inexplicable on purely mechanical grounds; that is to say, by means of figures and motions. Suppose there were a machine, so manufactured as to think, feel, and have perception: it might be imaginatively increased in size (while maintaining the same proportions) so that one might enter into it even as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception.**
The excerpt above captures with supreme clarity the explanatory gap out of which the hard problem of consciousness emerges as a logical consequence, just as Chalmers defined it in 1995. In what is sometimes called his “mill argument” for the immateriality of the mind, Leibniz points out that to seek for the mind’s contents amongst the brain’s workings is a misunderstanding of concepts. The source of this mistake is the expectation that thoughts should be accessible by the same means of investigation as material things. To Leibniz’s thinking, this is no less absurd than to expect to hear a candle, to photograph the sound of a cello, or, to use his example, to see the mind’s workings with the organs of external sensation.*** In the excerpt above, Leibniz’ is employing “perception” in the same manner as Chalmers used the words “consciousness” and “experience” in the quotes above, and the term “qualia” in other contexts. When Chalmers wrote, therefore, that “of thinkers in the recent and distant past…[who] recognized the particular difficulties of explaining consciousness and have tried to face up to them in various ways,” he most certainly meant to include Leibniz in their midst. Both Chalmers and Leibniz “face up” to the problem of consciousness by denying the existence of matter altogether in the Galilean-Cartesian sense. By positing that experience is inherent in all being, they close the explanatory gap by not creating it in the first place. Chalmers’ panpsychism and Leibniz’ monadology, despite their differences, explain ordinary human experience with the theory that it is aggregated out of atomic bits of experience. In the three centuries that separate these thinkers, however, panpsychism was unpopular to say the least, though it is experiencing a revival as thinkers attempt to “face up” to the problem. We will briefly return to these recent approaches later in this exploration. First, however, we must further attempt to understand the aetiology of the hard problem, affirming that a true remedy depends on a true diagnosis.
Perhaps no one so clearly articulated the spirit of natural science (even if he remained cagey as to the specifics of the method) as Francis Bacon of Verulam, Lord Chancellor and Viscount of St. Albans. “Natural science,” declared Bacon in 1605, “doth make inquiry, and take consideration of the same natures: but how? Only as to the material and efficient causes of them, and not as to the forms.” Bacon here draws on the Aristotelian distinction between morphē (μορφή (literally “shape” or “form”)) and hyle (ύλη (literally “wood” or “matter”)). Scholastic thinkers had elaborated this distinction under the Latin terms forma and materia, which Bacon referred to in their anglicised forms the quote above. Where Aristotle and the Scholastics distinguished these two aspects of a single substance, Bacon divides them and holds substance to be a purely material thing. Thus he continues his project, which by 1620 he conceived of as not merely an “Advancement of Learning” as in 1605, but as an “Instauratio magna,” a “Grand Instauration of the Sciences.” He sets forth his method in Book II:
Matter rather than Forms should be the object of our attention, its configuration and changes of configuration, and simple action, and laws of action or motion, for Forms are figments of the human mind, unless you call those laws of action forms.
After rejecting the notion of forms in the Aristotelian sense, Bacon replaces them with laws:
It may be that nothing really exists except individual bodies, which produce real motion according to law ; in science it is just that law, and the enquiry, discovery, and explanation of it, which are the fundamental requisite both for the knowledge and for the control of Nature. And it is that law, and its “ clauses,” which I mean when I use (chiefly because of its current prevalence and familiarity) the word “ forms.”
The substitution of laws for forms in the conception of nature is a change of immense significance. It is analogous to the difference between a regulation and a behaviour. To properly understand the import of Bacon’s decree, a brief excursion into Aristotelian physics is in order. Specifically, we will consider Aristotle’s notion of causality in order to understand how the formal causes mingle with the material ones, as sight to eye, or as soul to body, in all objects and entities.
* Brief Answer to Big Questions, 2018.
Google’s Zeitgeist Conference in Hertfordshire, 2011.
My own translation from Leibniz’s original, from section 14
** My own translation from Leibniz’s original, from section 14 of Monadologie:
Andererseits muß man gestehen, daß die Vorstellungen, und Alles, was von ihnen abhängt, aus mechanischen Gründen, dergleichen körperliche Gestalten und Bewegungen sind, unmöglich erklärt werden können. Man stelle sich eine Maschine vor, deren Structur so eingerichtet sei, daß sie zu denken, zu fühlen und überhaupt vorzustellen vermöge und lasse sie unter Beibehaltung derselben Verhältnisse so anwachsen, daß man hinein, wie in das Gebäude einer Mühle eintreten kann. Dies vorausgesetzt, wird man bei Besichtigung des Innern nichts Anderes finden, als etliche Triebwerke, deren eins das andere bewegt, aber gar nichts, was hinreichen würde, den Grund irgend einer Vorstellung abzugeben.
*** Or no less misguided, in the estimation of St. Thomas Aquinas, than the pedants who argue over the number of angels who can dance on the head of a pin:
Some, however, have been deceived in this matter. For some who were unable to go beyond the reach of their imaginations supposed the indivisibility of the angel to be like that of a point; consequently they thought that an angel could be only in a place which is a point. But they were manifestly deceived, because a point is something indivisible, yet having its situation; whereas the angel is indivisible, and beyond the genus of quantity and situation. Consequently there is no occasion for determining in his regard one indivisible place as to situation: any place which is either divisible or indivisible, great or small suffices, according as to his own free-will he applies his power to a great or to a small body. So the entire body to which he is applied by his power, corresponds as one place to him.
(Summa Theologica, 1.52.2)