We live with a fractured sense of self. In our modern, popular understanding, the mind is often presented as inherently divided, a house divided between two opposing faculties. On one side stands reason: slow, logical, cool-headed, and judicious. On the other stands emotion: fast, impulsive, hot, and irrational. This binary is so deeply embedded in our language and psychology that we treat it as a fundamental truth of the human condition, elevating it from a mere psychological theory to a pervasive cultural narrative.
This intuitive divide exceeds mere folk psychology; it has functioned as the dominant paradigm in formal philosophy and cognitive science. These disciplines have historically treated reason and emotion as "fully independent cognitive faculties" [1]. This framework allowed for a clean separation, suggesting their respective causal contributions to any given thought or judgment could be neatly isolated.
But this comfortable division is dissolving. In recent decades, a "revolution in the science of emotion" has begun, one that is creating a "paradigm shift" in how we understand decision-making [2]. This new wave of research reveals that emotions are not irrational static; rather, they are "potent, pervasive, predictable... drivers of decision making". Neuroscience, too, has moved past a simple cause-and-effect model. It is increasingly moving toward an integrated view where a feeling and its biological expression are not a sequence, but two phases of the same unbroken activity [3].
This contemporary scientific "paradigm shift", however, is effectively a restoration. The very "problem" that modern science is "solving" - the idea of a disembodied reason at war with a chaotic emotion - is often treated as a timeless psychological fact. While the roots of this divide run deep in Western thought—from Plato’s Charioteer to Cartesian dualism—the antagonistic "war" metaphor was forcefully radicalized in the modern era. The "traditional rational choice theory" that new research is now "synthesizing" with emotion is not the original philosophy of the 18th century. It is the caricature of it. If this split is not a scientific absolute, we must ask: why does it feel so inescapable? This chapter argues that while the binary pre-existed, it was re-popularized and hardened by a highly effective act of historical branding, a moment when one intellectual movement weaponized an ancient split to manufacture its own opponent.
The story of our fractured self begins with the movement that centered on the importance of emotion: Romanticism. Originating in Europe near the end of the 18th century, the Romantic movement emerged, in part, in direct reaction to the preceding era. It was conceived as a response to 18th-century rationalism.
To articulate this new vision, the Romantics contrasted it with a clear antagonist. They defined the preceding era as an "ordered world of Enlightenment thought" - one obsessed with "rationalism and classicism," order, calm, harmony, and balance.
Against this "ordered world," Romanticism championed distinct values: the individual, the subjective, the imaginative, and the spontaneous. It placed a premium on distinct forms of intuitive reason and individual experience above the perceived coldness of logical calculation. This created a simplistic but potent binary. In a famous encapsulation of this critique, the "man of the enlightenment" looks at a rainbow and, like Newton, "break[s] the rainbow down into its constituent parts," destroying its magic. The "romantic," by contrast, is "transfixed by its beauty" [4].
This critique was a specific and powerful argument. To give this intellectual contrast a name, a label was elevated and popularized: "The Age of Reason". But this label, which we now often take as a neutral historical descriptor, was partly a rhetorical construction - emphasizing certain strands of Enlightenment thought (Continental rationalism, French materialism) while obscuring others (Scottish sentimentalism, English empiricism).
This is not to say the Romantics invented their opponent from whole cloth. There were genuine targets for their critique: the mechanistic philosophy of La Mettrie, the rigid systematizing of certain German rationalists, the confident universalism that could shade into cultural imperialism. The error lies not in the Romantic critique itself, but in our retrospective acceptance of their framing as the complete picture. The Enlightenment contained multitudes; the Romantics, for understandable polemical reasons, flattened it. We need not repeat their simplification.
This caricature was so successful that it has been accepted by both modern defenders and detractors of the Enlightenment [6]. Both those who call for a "reboot of the Enlightenment" to defend science, and those who see it as a "pathology" that leads to domination, make the same "collective error": they both accept "that the Enlightenment was a movement of reason opposed to the passions". They are, in effect, arguing over a phantom. The Enlightenment was not solely about science - it was about human wellbeing in many forms and an opposition to superstition.
The first step in dismantling this phantom is to look at the label itself. The "Age of Reason" is a deeply misleading name for the 18th century. As the Stanford Encyclopedia of Philosophy notes, while there was an "enthusiasm for reason," this enthusiasm was not primarily for "the faculty of reason as an independent source of knowledge." That concept, a holdover from 17th-century rationalism, was, in fact, "embattled" during the 18th century [7].
The intellectual movement in the ascendant was not pure rationalism, but empiricism. We must distinguish between the "rationalist strain" founded by René Descartes-which prioritized a priori reason and innate ideas-and the "empiricist strain" championed by John Locke and David Hume. While the former, along with certain French materialists, did advance a more mechanistic view of the universe that the Romantics rightfully critiqued, it was the empiricist strain that came to dominate the Anglophone Enlightenment.
This empiricist strain, which became the dominant force in the Enlightenment, argued the precise opposite of the "cold reason" caricature. It argued that all knowledge "originates from sensory experience". John Locke, a foundational Enlightenment thinker, wrote his An Essay Concerning Human Understanding as a direct assault on the rationalist doctrine of innate ideas. For Locke, the mind is a tabula rasa, a "blank piece of paper" [8]. All of its ideas, without exception, come from "experience," which he defined as either "sensation" (perceiving the external world) or "reflection" (perceiving the operations of our own minds).
cold light of reason and the warm fire of meaning.
While Hume and Smith were attempting to re-integrate reason and feeling in the 18th century, they were doing so against a backdrop of deep cultural trauma. Their 'Sentimental Empiricism' was not just a theory; it was a rescue operation for a civilization that had recently been torn apart by the very 'passions' they sought to refine. It is an "experience-first" philosophy that, by its very nature, demands engagement with "the physical world". Locke's empiricism is considered "paradigmatic of the ideals of the Enlightenment" precisely because it insists on "evidence" and "empirical observation". This "bottom-up" approach, exemplified by Bacon and Newton, was the era's defining feature, not the "top-down" metaphysics of the rationalists.
The central Romantic critique-that the Enlightenment "disregarded human emotions, imagination, and the complexities of individual experience"-is thus aimed at the wrong target. The actual Enlightenment was founded on experience. The Romantics were not introducing experience to a movement that had ignored it; they were re-interpreting it. They disliked the conclusions the empiricists drew from experience (such as a "mechanistic" understanding of the universe), and so they championed a different kind of experience - subjective, emotional, and sublime - over the sensory, observable, data-driven experience of the empiricists. To claim the Enlightenment ignored experience is the foundational distortion of the strawman.