Rene Descartes asked the right question. He wanted to know what can be said about reality with certainty once all tradition, all authority, and all habit are set aside. In his Meditationes de Prima Philosophia (Descartes, 1641), he radicalised doubt to the limit of the thinkable: perhaps the senses deceive me, perhaps there is no external world, perhaps everything is a dream. Only one thing survived this trial: thinking itself. Cogito, ergo sum — I think, therefore I am. When you hear this sentence for the first time, it sounds like a liberation: solid ground at last. Here begins modern philosophy. And here begins its undoing.
#The Cut That Dismembered the World
What Descartes gained with the cogito was certainty at the cost of an amputation. To secure the thinking self as indubitable, he had to exclude everything non-thinking from the realm of the certain. Thus arose his notorious division: res cogitans, the thinking substance, and res extensa, the extended, purely material substance. Mind here, matter there, and between them an abyss that three centuries of philosophy could not bridge. The body you inhabit, the breath you are drawing right now, the sensation that connects you with the room — all of this falls, in Descartes, on the side of mere extension, of mindless mechanics.
Schelling identified the consequences of this cut more clearly than anyone. In his Munich lectures Zur Geschichte der neueren Philosophie, he wrote: Descartes saw in the corporeal only the opposite of the spiritual and thinking, without considering it possible that one and the same principle might exist in matter merely in a state of its degradation, and as spirit in a state of its exaltation (cf. Schelling, 1827). For Descartes, matter was absolutely dead, absolutely mindless — something produced, with nothing of the producing principle in it.
#What Follows From Dead Matter
A philosophy that splits the cosmos into dead stuff and disembodied mind generates problems it cannot solve on its own. Descartes could never explain how mind and body interact. His attempt via the pineal gland failed to convince even his contemporaries. Schelling remarked that Descartes appears in philosophy almost only to offer another mind the foundation for an entirely different system (cf. Schelling, 1827). His occasionalism — falling back on God as the perpetual mediator between body and soul — was so philosophically unsatisfying that it practically forced Spinoza’s counter-position into being.
The practical consequences extend far beyond academic philosophy. Descartes defined animals as mechanical automata. Gwendolin Kirchhoff drew the connection in her debate with Joscha Bach (2026): if you define a living being as a machine, then it simply squeaks like a machine when you cut it open alive. Vivisection did not follow from the Cartesian metaphysics by accident. Where the living is mindless by definition, there is no philosophical reason not to treat it as material. That this logic extends into the current debate on machine consciousness is no coincidence: anyone who conceives the cosmos as a machine can, conversely, ask whether machines might be conscious.
#Schelling’s Diagnosis
Schelling recognised in Descartes both the necessary new beginning and the fatal error. Descartes was right to move beyond everything received, to dare the absolute fresh start. He was, as Schelling wrote, revolutionary in the spirit of his nation — yet philosophy regressed with him into a second childhood, a kind of immaturity that Greek philosophy had already outgrown with its very first steps (cf. Schelling, 1827).
Schelling’s deepest critique concerns not the cogito itself but its reach. The cogito proves only: I am in a certain way, namely as thinking. Nothing more follows. If you read the sentence closely, you notice: neither does an unconditional I-am follow, nor a certainty about the external world that would then have to be secured through a proof of God. Schelling showed that the entire detour Descartes took via the ontological argument for God’s existence collapses under a logical error: from the premise that the most perfect being can only exist necessarily, it does not follow that it exists — only that it necessarily exists if it exists (cf. Schelling, 1827). You can turn this argument in either direction without altering its structure: it remains circular.
#The Mind That Forgot Itself
The real legacy of Descartes lies not in a single argument but in a turning point. By tearing apart what belongs together — matter and mind — he destroyed, as Schelling put it, the great general organism of life and surrendered both the lower and the higher to a dead, merely mechanical view that remained dominant almost to the present day (cf. Schelling, 1827).
In natural philosophy lies the counter-position: nature and mind are not two substances requiring a bridge, but one reality that presents itself differently to different ways of looking. Schelling articulated this thought in 1797 in his Ideen zu einer Philosophie der Natur, and Jochen Kirchhoff (1944-2025) radicalised it: what is supposedly dead matter can never be grasped as an absolute absence of life, only as extinguished life, as the residue of a prior process (cf. Kirchhoff, J., 2003).
Descartes nonetheless remains a key to understanding modernity. Not because his answers hold, but because his error was so consequential that one must know it to grasp the situation. The mind-body problem, the hard problem of consciousness, the entire debate on consciousness and AI: they all move within the rift Descartes laid open. If you wonder why AI research seriously discusses whether machines might have consciousness, you stand in the middle of the Cartesian dualism’s legacy: once you have split the world into dead stuff and disembodied mind, you can tentatively reinsert the mind into the stuff — into silicon instead of brain tissue. The task of philosophy after Descartes is not to build better bridges across this rift, but to understand that it never had to exist.
#Sources
- Descartes, R. (1641). Meditationes de Prima Philosophia.
- Schelling, F. W. J. (1827). Zur Geschichte der neueren Philosophie. Stuttgart: J.G. Cotta.
- Kirchhoff, J. (2021). Nikolaus Kopernikus. Ch. “Zur Konzeption und Kritik der mechanistischen Weltauslegung”.
- Kirchhoff, J. (1991). Anti-Geschichte der Physik: Neue Vorstellungen ueber die Natur. edition dionysos.