This Day in Philosophy — 31 August: Helmholtz born, Baudelaire dead

The calendar sets two names side by side today, and the connection between them is not visible at first glance.

Hermann von Helmholtz was born at Potsdam on 31 August 1821. Charles Baudelaire died in Paris on 31 August 1867.

The real link is not in the date: both were born in 1821. One in April, the other in August. And both worked at the same question, in different languages: what exactly is it that modern man sees?

Helmholtz: taking Kant into the laboratory#

Helmholtz had the broadest reach of any figure in nineteenth-century science. Physiologist, physicist, mathematician and philosopher.

He contributed to the formulation of the principle of the conservation of energy. He measured the speed of the nerve impulse — which until then had been thought too fast to be measured at all. He invented the ophthalmoscope, and with it ophthalmology gained the power to see inside the eye. On colour vision, on hearing and on sound he did founding work.

But his place in the history of philosophy does not come from those discoveries.

Helmholtz was one of the leading figures of the movement of return to Kant — zurück zu Kant. And he made the return not by defending Kant as he stood, but by testing him against the findings of experimental science.

The sign theory of perception#

The doctrine taken as Helmholtz's signature is the sign theory of perception.

The problem starts here. When we see a red, what happens in the eye is a response of the nervous system to a stimulus of a particular wavelength. What sort of relation, then, holds between that response and the object outside?

The classical answer says resemblance: perception is a copy of the object.

Helmholtz rejected it. Our sensations are not the copies of objects but their signs. A sign need not resemble what it indicates — any more than the word "table" resembles a table.

The move has wide consequences. For once we grant that perception does not resemble the object, we have to explain how we get from perception to object at all. Helmholtz's answer is unconscious inference: the mind infers objects from sense data by means of rules built up out of habit and experience. Seeing is in fact a piece of reasoning carried out without our noticing it.

A hundred and fifty years later, the concept is still alive in the predictive processing models of cognitive science.

The quarrel with Kant#

Helmholtz's allegiance to Kant grows complicated at this point.

For Kant, space is not a concept drawn from experience; it is the a priori form of experience. And that form is Euclidean. We cannot represent space to ourselves in any other way.

Helmholtz objected on two fronts.

The physiological front: how our perception of space is built up can be examined experimentally — and the examination shows the perception of space to be a learned capacity.

The mathematical front: non-Euclidean geometries are consistent. Helmholtz devised his famous thought experiments describing how beings living in spaces of constant curvature would experience their worlds. The conclusion: Euclidean space is not a necessary form of thought.

What follows from this is a serious departure from Kantianism. Helmholtz made the a priori dependent on the findings of natural science. That is: experience has conditions, but what those conditions are is decided by science, not by philosophy.

This is the tension at the founding of neo-Kantianism. Lambert's work on the parallel postulate, which this column noted a few days ago, was an early link in the same chain.

Influence: the road to Vienna#

Helmholtz's sign theory flowed straight into the philosophy of the twentieth century.

Moritz Schlick — the founder of the Vienna Circle — took the doctrine over and transformed it, turning the Kantian understanding of the intuition of space into an empiricist version of the causal theory of perception. The account of perception in logical empiricism comes largely down this line.

Ernst Cassirer, Hermann Cohen and the whole of the Marburg School, moreover, were founded in a reckoning with Helmholtz.

Helmholtz's real legacy is perhaps this: he showed that epistemology could enter the laboratory. That thinking about the conditions of knowledge is not work to be done in an armchair.

Baudelaire: the invention of modernity#

On the same day, in 1867, Charles Baudelaire died in a hydropathic clinic in Paris. He was forty-six; he had spent his last two years paralysed and aphasic.

Baudelaire was not a philosopher. But he left philosophy a concept: modernité.

He was the first to use the word in its present sense, in the essay of 1863, The Painter of Modern Life. His definition ran thus: modernity is what is "transient, fleeting, contingent" in art — the other half of art being the eternal and the immutable.

The radicalism of that definition is easily missed. Until Baudelaire, beauty was something seized in spite of transience. Baudelaire placed beauty inside transience.

City, crowd, gaze#

Baudelaire's lasting contribution to philosophy is his description of the setting of modern experience: the great city.

The Flowers of Evil (1857) was written inside the Paris that Haussmann was rebuilding. Quarters torn down, boulevards driven through, glass-roofed arcades, gas lamps, crowds.

In that setting Baudelaire defined a new figure: the flâneur — the observer who wanders the crowd without purpose, who looks but does not join.

Once the figure reached the hands of Walter Benjamin, it turned into a method. Benjamin's unfinished Arcades Project grew out of his reading of Baudelaire, and was an attempt to construct a phenomenology of nineteenth-century capitalism. Adorno, Kracauer and the whole of Frankfurt School cultural analysis pass down this line.

Two men of 1821#

The paths of Helmholtz and Baudelaire never crossed. But they stand at the two ends of a single problem.

Helmholtz asks: how does the eye see? His answer is physiological — sensation is a sign, perception an unconscious inference. The modern subject's relation to the world is indirect, and the mechanism of that mediation can be investigated.

Baudelaire asks: what does modern man look at? His answer is aesthetic — at the transient, at the crowd, at the street. And the gaze itself establishes a new form of experience.

In fact the two are saying the same thing: seeing is not innocent. Vision is neither a passive copying of the object nor a neutral record. It is a constructed, learned, historical act.

The thesis reaches as far as Don Ihde's theory of technological mediation and the argument that algorithms determine what we are able to see, both of which we took up this month.

A question asked a century ago is being asked again today, in front of a screen.

In Turkish#

Helmholtz's texts are thin on the ground in Turkish; they survive in fragments in anthologies of the philosophy of science. Baudelaire's The Flowers of Evil, Paris Spleen and The Painter of Modern Life have been translated into Turkish many times over. Benjamin's writings on Baudelaire are available in Turkish as well.