Descartes' Dangerous Idea
Bifurcation & the foundation of the scientific worldview
Historians of thought are in general agreement that the philosophy of Rene Descartes marks a turning point that inaugurates the beginning of modern philosophy. Descartes’ mind/body dualism would cast a long shadow over subsequent philosophers, who would adopt various strands of idealism, materialism and dualism to try and make sense of (or do away with) this split. What is less recognised is that Descartes also inaugurated a second, more radical split, one which became so influential on the modern mind it is difficult for us to even recognise.
As well as separating mind and matter, Descartes bifurcates the world out there into res extensa and res cogitans. Res extensa is the world bereft of sensory qualities, namely the quantitative, extended aspect of objects accessible to science. The world as we perceive it - the red of the apple, the green of the tree, the scent of the rose - is res cogitans, the mental and subjective aspect of reality which is inaccessible to science. We can see how this lends itself to all kinds of subjectivism.
This division is what the 20th century philosopher Alfred North Whitehead calls bifurcation. In the words of Bruno Lautour:
“Bifurcation is what happens whenever we think the world is divided into two sets of things: one which is composed of the fundamental constituents of the universe— invisible to the eyes, known to science, yet real and valueless—and the other which is constituted of what the mind has to add to the basic building blocks of the world in order to make sense of them"
What is being bifurcated is primary and secondary qualities, a distinction which would become central to the worldview of later philosophers (the primary/secondary quality distinction is central to the epistemology of Locke.)
This distinction was not an innovation by Descartes, but the revival of an old postulate of materialism: As early as the 4th century BC the atomist Democritus wrote that
"By convention there are sweet and bitter, hot and cold, by convention there is colour; but in truth there are atoms and the void"
And, shortly before Descartes, Galileo wrote that “tastes, odors, colors, and so on … reside only in the consciousness”. But it was Descartes that gave bifurcation a fuller metaphysical explication. Descartes was committed to replacing the Aristotelian assumptions of western thought and instead founding a theoretical basis for a mechanical science on mathematical principles. Of course, only a mechanical universe could be understood by a mechanical science, and the genius Descartes recognised that in that case all of the qualitative, phenomenological aspects of reality could not be accounted for:
“We can easily conceive how the motion of one body can be caused by that of another, and diversified by the size, figure and situation of its parts, but we are wholly unable to conceive how these same things (size, figure and motion), can produce something else of a nature entirely different from themselves, as, for example, those substantial forms and real qualities which many philosophers suppose to be in bodies .”
Thus, the endeavour of a successful mechanical account of the universe necessitated bifurcating and demoting res cogitans to a secondary, private phantasm. Descartes here laid the foundations for the worldview that would overturn the Aristotelian/Thomist assumptions of the Middle Ages and make philosophical knowledge secondary to physics. Medieval scholasticism inherited an essentialism from classical philosophy which viewed an objects’ qualities as inseparable from the essence of the object. Separating, and subjectivising the secondary qualities of res cogitans was thus a radical break with what had come before.
In the Middle Ages:
“Not only did the world exist for the use of man, but it was also fully intelligible by the senses and in relation to the human uses of that world. The basic categories of this thought, of Aristotelian-Thomistic inspiration, were those of substance, essence, matter, form, quantity and quality. Such categories have, in modern thought, been replaced by time, space, mass, energy, etc., while quantity gains preeminence over quality.”
The bifurcation premise was picked up by Newton. He incorporated this assumption into his Principia, which would form the basis for the scientific worldview. Newton's laws of motion provided a complete mathematical framework to describe the behaviour of physical bodies. The basic picture of things presented by Newton, which was seen to confirm the mechanical theory of the universe, became the basis of the scientific worldview which informed later philosophers and scientists alike. It is only since the 20th century that the problems of bifurcation have been seriously interrogated, but it continues to operate as a background assumption to most scientists and forms the basis for the still popular understanding of the universe as mechanism.
But since bifurcation was never and could never be demonstrated, why is it so hard for modern thinkers, especially scientists, to now think outside of it? While the bifurcationist approach to the study of the natural world does not necessitate a reductionist or scientistic worldview, and the scientific method is itself ontologically neutral, it is built on a methodological reductionism. From the practical starting point of assumed bifurcation and the limiting of knowledge to what can be expressed quantitatively, it is a small leap to turn this methodological assumption into a general rule, and outright deny the existence of any knowledge outside of its scope. One often observes among scientific thinkers that what are useful rules of methodology for a scientist (parsimony, verificationism) become for them general rules of ontology. And so it is for bifurcation: what began as a tacit ontology in the background of the scientific worldview has become explicit with the common affirmation of scientism/materialism as dogma today.