The extraordinary fruitfulness of modern scientific method was achieved, before all else, by a severe narrowing of investigative focus; and this involved the willful shedding of an older language of causality that possessed great richness, but that also seemed to resist empirical investigation. The first principle of the new organon was a negative one: the exclusion of any consideration of formal and final causes, and even of any distinct principle of “life,” in favor of an ideally inductive method purged of metaphysical prejudices, allowing all natural systems to be conceived as mere machine processes, and all real causality as an exchange of energy through antecedent forces working upon material mass. Everything physical became, in a sense, reducible to the mechanics of local motion; even complex organic order came to be understood as the emergent result of physical forces moving through time from past to future as if through Newtonian space, producing consequences that were all mathematically calculable, with all discrete physical causes ultimately reducible to the most basic level of material existence. And while, at first, many of the thinkers of early modernity were content to draw brackets around physical nature, and to allow for the existence of realities beyond the physical—mind, soul, disembodied spirits, God—they necessarily imagined these latter as being essentially extrinsic to the purely mechanical order that they animated, inhabited, or created. Thus, in place of classical theism’s metaphysics of participation in a God of infinite being and rationality, they granted room only for the adventitious and finite Cosmic Mechanic or Supreme Being of Deism or (as it is called today) Intelligent Design Theory. But, of course, this ontological liberality was unsustainable. Reason abhors a dualism. Any ultimate ground of explanation must be one that unites all dimensions of being in a simpler, more conceptually parsimonious principle. Thus, inevitably, what began as method soon metastasized into a metaphysics, almost by inadvertence. For a truly scientific view of reality, it came to be believed, everything—even mind—must be reducible to one and the same mechanics of motion. Those methodological brackets that had been so helpfully drawn around the physical order now became the very shape of reality itself.
It was always something of a fantasy, of course. For one thing, even as a method, the mechanical model extends only so far. Pure induction is an impossible ideal. In the life sciences, for instance, organisms can only very rarely be investigated without any hypothetical appeals to purpose whatsoever, or without treating organic structures as intentional systems; and it is only a metaphysical prejudice that dictates that explanations referring to purpose are no more than a useful and dispensable fiction. Moreover, before “higher causes” like form and finality could be excised from the grammar of the sciences, they had first to be radically misconstrued. Even such residual Aristotelian terminology as remained in the sciences had already, by the late sixteenth century, been mechanized, so to speak. One need only read Francis Bacon to confirm this. Form and finality had come to be seen as physical forces or influences extrinsic to a material substrate that in itself was not the pure potentiality of “prime matter” but merely a universal, subtle, ductile, unarticulated physical substance. The elements of nature were not imagined, as they had been in the classical and mediaeval synthesis, as having an intrinsic disposition toward order or vital integrity; they were seen simply as inert ingredients upon which formal determinations were adventitiously impressed, under the external guidance of final causes that operated merely as factitious designs. And so, seen thus, form and finality soon came to seem not only superfluous suppositions, but little more than features of an inferior and obsolete mechanical model.
But, of course, one cannot really reject something one does not understand. Neither Aristotle’s concept of an aition, nor any scholastic concept of a causa, actually corresponds to what we—following our early modern predecessors—mean when we speak of a “cause.” A better rendering of aitia or causae, in the ancient or medieval sense, might be “explanations,” “rationales,” “logical descriptions,” or (still better) “rational relations.” The older fourfold nexus of causality (Aristotle’s material, efficient, formal, and final causes) was not, that is to say, a defective attempt at modern physical science, but was instead chiefly a grammar of predication, describing the inherent logical structure of anything that exists insofar as it exists, and reflecting a world in which things and events are at once discretely identifiable and yet part of the larger dynamic continuum of the whole. It was a simple logical picture of a reality in which both stability and change can be recognized and described. And these aitia or causae were intrinsic and indiscerptibly integral relations, distinct dimensions of a single causal logic, not separated forces in only accidental alliance. A final cause, for instance, was an inherent natural end, not an extrinsically imposed design; and this was true even when teleology involved external uses rather than merely internal perfections (as in the case of human artifacts); it was at once a thing’s intrinsic fullness and its external participation in the totality of nature. Thus, in the Liber de Causis (that mysterious digest and theological synthesis of the metaphysics of Proclus that entered Western scholasticism from the Islamic philosophical world) one of the principal “causes” of any isolated substance is the taxonomic category in which that thing subsists, the more “eminent” rational structure to which it belongs. In a sense, a causal relation in this scheme is less like a physical interaction or exchange of energy than it is like a mathematical equation, or like the syntax of a coherent sentence. Admittedly, this is a picture of reality that comes from ages in which it was assumed that the structure of the world was analogous to the structure of rational thought. But, then again, this was an eminently logical assumption—if only because there appears to be a more than illusory or accidental reciprocal openness between mind and world, and because the mind appears genuinely able to penetrate the physical order by way of irreducibly noetic practices like mathematics and logic.
In any event, perhaps it really was necessary to impose the discipline of this impoverished causal language upon the scientific intellect, if only to direct its attention to the finest and humblest of empirical details. But even so, as Hegel so brilliantly demonstrated, one can never really reason purely from the particular. Once the notion of causality has been reduced from an integral system of rationales to a single kind of local physical efficiency, it becomes a mere brute fact, something of a logical black box; description flourishes, but only because explanation has been left to wither. So it was that Hume, having seen the spectral causal agencies of the schoolmen chased away, found causality itself now to be imponderable, logically reducible to nothing but an arbitrary sequence of regular phenomenal juxtapositions; even mathematical descriptions of events now became nothing more than reiterations of an episodic narrative without clear logical necessity. And this is indeed where we remain. Wherever induction fails to provide us with a clear physicalist narrative for especially complex or exceptional phenomena (like life or consciousness), we now must simply presume the existence and force of physico-mechanical laws sufficient to account for the emergence of such phenomena; and we must, moreover, do so no less casually and vaguely than those schoolmen of old supposedly presumed “obscure” or “occult” formal and final causes. We are no less dogmatic than our ancestors; we merely have fewer clear reasons for the dogmas we embrace. The older physical logic was coherent, though speculative; the newer is incoherent, though empirical. When mechanistic method became a metaphysics, and the tinted filter through which it viewed nature was mistaken for an unveiling of its deepest principles, all explanations became tales of emergence, even in cases of realities—life, consciousness, even existence itself—where such tales seemed difficult to distinguish from stories of magic.
Nowhere is the essential arbitrariness of this picture of reality more obvious than in the alleged principle of the “causal closure of the physical”—the principle that there simply cannot be any kind of “causality” in nature other than brute material forces—which is so often invoked as a scientifically established truth, on the rather thin basis of the fixed proportionality of matter and energy in the universe, but which is merely a metaphysical dogma, and one that even otherwise sophisticated theorists often translate into the crudest kind of physical determinism. I have known learned physicists who still talk as if something like Laplace’s fantasy holds true: a demon of superlative intelligence, knowing at a given instant the precise location and momentum of every atomic particle in existence, could both reconstruct the entire physical history of the universe and foresee its entire future. True, these physicists might all have granted that statistical thermodynamics probably dictates that this would not be literally possible; but still they spoke as if, in principle, all events at higher levels of physical organization must be reducible—without remainder—to lower, more particulate causal moments. Hence, if our demon could somehow account for irreversibility or quantum indeterminacies—maybe by a perfect grasp of maximum entropy thermodynamics or by an occult knowledge of quantum hidden variables—he could, from the dispositions of all the atoms and molecules composing me and my environment last Wednesday at noon, have infallibly predicted my presence here today, because everything we do is the inevitable macroscopic result of the ensemble of impersonal physical forces underlying our formal existence.
Then again, perhaps one need not look either to molecular and evolutionary biology or the phenomena of mental life to see that the mechanical model of nature is defective. Really, perhaps, it is enough simply to consider the seemingly indivisible relation that exists between them in the very encounter between nature and mind: the intelligibility of the world and the power of thought to lay hold of it. Perhaps all we need consider is how the inherently formal and intentional structure of rational thought seems to correspond so fruitfully to the rational structure of the world. This by itself invites us to reconsider something at least like the causal language proposed in the Aristotelian tradition, in which (again) nature’s deepest rational relations are more like the syntax of a sentence, or mathematical equations, than like mere accidental concrescences of physical forces. Perhaps modern prejudice has the matter backwards; perhaps it is mechanism that should be regarded as the dispensable methodological fiction, while the purposive language we use to isolate specific organic functions is the true reflection of reality. Perhaps mechanistic models never were anything more than artificial constraints, by which discrete processes might be prescinded from a whole that, in itself, has something like the structure of intentional thought. After all, it is absurd to think that a model created by the willful exclusion of all mental properties from our picture of nature could then be used to account for the mental itself; and yet the mental is quite real, and quite at home within the natural order. If, then, one presumes a reductively physicalist model of all reality, but is then confronted by any aspect of nature that, as in the case of consciousness or intentionality, proves utterly resistant to mechanical description, the only responsible course of action is to abandon or suspend the model in regard to the whole of nature. If the phenomenon cannot be eliminated, the model is false.
Nor can we stop there. Once again, a certain principle of logical parsimony asserts itself here, and then invites or even obliges us completely to reverse our original supposition. Reason abhors a dualism, as I have said; ideally all phenomena should be reducible to a single, simpler, more capacious model of reality. Far from continuing to banish mind from our picture of nature, then, perhaps we should reconsider the ancient intuition that nature and mind are not alien to one another precisely because nature already possesses a rational structure analogous to thought. Perhaps the ground of the possibility of regular physical causation, in the energetic and mechanical sense, is a deeper logical coinherence of rational relations underlying all reality; and hence mind inhabits physical nature not as an anomaly, but as a revelation of the deepest essence of everything that exists. The intentionality of mind then is neither a ghostly agency inexplicably haunting a machine, nor an illusion reducible to non-intentional and impersonal forces, but instead the most intense and luminous expression of those formal and teleological determinations that give actuality to all nature. What makes us believe we should—or, for that matter, can—think otherwise?
What difference might all this make for the sciences, practically speaking? Little or none, really. The sciences need not aspire to total exhaustive explanation; they are often most powerful when they consist largely in local and narrow investigations, and then in theoretical interpretations of very particular discoveries. For the culture of the sciences, however, as well as for a true consonance (rather than a mere amicable segregation) between the sciences and theology, it could scarcely be more consequential. For one thing, it is always salubrious to be reminded of the limits of our methods; and, for anyone committed to the search for truth, it is always wise to think about the universal frame of reality within which one’s investigations take place. If one does this, one may approach a place where the deepest aspirations of the sciences and the most essential affirmations of theology prove to be both irresistibly apposite. When we think seriously about the complex rational structure of reality and the way in which it seems to be reflected in the structure of rational mind, we enter the realm of spirit, of intellect, of a formal and final logic in nature already analogous to mind or rational thought. Perhaps only for this reason can the veil of Isis be lifted, and nature be revealed to mind, and perhaps it is also only for this reason that mind can inhabit nature. Here the physical sciences themselves urge us toward a certain metaphysical supposition. It may be that, pursued to its logical terminus, the very enterprise of scientific reasoning suggests or even secretly presumes that the being of the world—the ontological horizon within which it takes shape and exists—is something like an act of thought. Here the questions of science and those of theology converge upon the same mysteries, not through some maladroit confusion of two incompatible kinds of causal narrative (the cosmological and the ontological, say), but quite naturally, because the very concept of causality itself still demands for itself the full richness of all its possible logical acceptations. No physical science can answer or explain away the mysteries that here come into view; neither can any theology; but both would do well to recognize the threshold upon which they stand.
All the labors of the scientific intellect are undertaken within the embrace of a structure of intelligibility that the sciences need not pretend to understand, penetrate, or encompass, but that nevertheless sustains them in all their labors. That intelligibility is the transcendental horizon toward which they necessarily strive, even when they hew faithfully to the limits of their proper remit. It shows itself to be nothing other than that original experience of the radiant mystery of being that first awakens the desire for truth, but now translated into a fixed orientation of the rational will. The sciences venture all their energies upon the reality of this ultimate rational intelligibility—upon the wager that the world’s being and its structure of rational order are one and the same event. Thus they undertake their perpetual journey toward an end that perhaps, in principle, they cannot reach: to disclose a perfect reciprocal transparency between mind and world, and hence an ultimate reality where existence and perfect intelligibility are convertible with one another because both subsist in a single unrestricted act of spiritual intelligence. This, in theological terms, is one of the paths of the mind’s journey into God. And this is also, at least in its ultimate intentions, a place where the consonance of scientific and theological reasoning is restored, on the far side of a provisional separation that at times has become an alienation. Both pursuits set out originally upon their different paths from the same innocent instant of existential amazement, and both together end, after all their several peregrinations, at a place where description fails, but where that primordial wonder finds its final consummation in wisdom: the threshold of that mystery—the cause of causes, the explanation of explanations, the holy of holies—toward which both are forever turned. And, however different the paths by which they have reached this sanctuary, each approaches it at the end ideally not as a stranger in a far country, but as a pilgrim entering a long-sought holy land.
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