|Immanuel Kant: still out of space and time?|
As Max Horkheimer and Theordor Adorno put in Dialectic of Enlightenment (1944/1969), "Kant combined the doctrine of thought's restlessly toilsome progress toward infinity with insistence on its insufficiency and eternal limitation." (Edmund Jephcott translation, 2002)
A key limitation of the ego's ability to perceive objects has to do with the categories that the human mind imposes on its perceptions. For Kant, time and space were both such qualities. Subjective qualities, in other words, rather than objective qualities of external reality.
Albert Einstein in his theory of special relativity explained that spacetime was a quality of the universe itself. Quantum physics revealed some aspects of subatomic reality that weren't fully compatible with Einstein's theories. But Einstein's theories are still "operative." They still explain observed reality, if not all its quantum features.
As Horkheimer and Adorno argue, science has set itself the task of infinite mastery of external nature. Whatever caution against hubris Kant's conception contained, the science of the 19th and 20th centuries developed in the direction of seeking total knowledge for asserting total dominance over nature:
Both subject and object are nullified. The abstract self, which alone confers the legal right to record and systematize, is confronted by nothing bur abstract material, which has no other property than to be the substrate of that right. The equation of mind and world is finally resolved, but only in the sense that both sides cancel out. The reduction of thought to a mathematical appararus condemns the world to be its own measure. What appears as the triumph of subjectivity, the subjection of all existing things to logical formalism, is bought with the obedient subordination of reason to what is immediately at hand.This approach, they argue, is focused on the "abstract spacial-temporal relationships" of objects "by which they can then be seized" by human perception and hands. It reduces knowledge to "mere perception, classification, and calculation."
But old Kant may not be out of the game yet. For one thing, we know much more today about the concrete physical mechanisms in human perception, which take us far from David Hume's view of the ego being basically the passive recipient of raw empirical perceptions from the outside, a view that heavily influenced Kant. Hegel wrote that Hume's historical notability was the fact that "Kant really took the starting point of his philosophy" from Hume. (Vorlesungen über die Geschichte der Philosophie II.1.C.2.A.2, 1908, my translation) Where Hume recognized that the ego formed empirical impressions into concepts, he believed that such concepts directly reflected the empirical data, although in a weaker form. But the complexity of the physical mediations between the empirical phenomenon and the formation of a human concept of them could be an argument on the side of the unknowability of the thing-in-itself.
The human reception of information isn't mediated only by concepts. Those impressions take a physical path to the brain for such concepts to be formed. Charles Liberman explains the path of sonic perceptions to the brain in Hidden Hearing Loss Scientific American 313:2 Aug 2015:
Hearing begins as the outer ear funnels sound waves through the ear canal to the eardrum, which vibrates and sets the bones of the middle ear in motion. The resulting vibrations then make their way to the inner ear’s fluid-filled tube, the cochlea — the location of hair cells that occupy a spiraling strip of tissue called the organ of Corti. These cells get their name from hairlike protrusions known as stereocilia that extend in bundles from one end of the cells. Hair cells most sensitive to low frequencies lie at one end of the cochlear spiral, and those most sensitive to high frequencies lie at the other end. As sound waves bend the “hairs,” these cells convert vibrations to chemical signals, emitting a neurotransmitter molecule — glutamate — at the other end, where the hair cells form synapses with the fibers of the auditory nerve.So, between raw empirical perception and a concept in the mind, the sound signal has to go through the outer ear, the ear canal, the eardrum, the middle ear's bones, the coclea and its Corti organ, and the chemical signals created by the coclea's hairs that form glutamate that stimulate the synapses that transmit the signal to the auditory nerve, which in turn transmits it to the brain, where the brain stem, midbrain, thalmus and auditory cortex using various chemical processes to allow it to turn it into a concept. This doesn't prove the unknowability of Kant's thing-in-itself. But it is a reminder of the physical components of human perception.
At the synapse, the glutamate released from a hair cell crosses a narrow cleft to bind to receptors on the end, or terminal, of an auditory nerve fiber. Each terminal is at one end of a nerve cell that extends a long fiber, an axon, to its other end in the brain stem. Glutamate bound to nerve fibers triggers an electrical signal that travels the entire length of the auditory nerve to the brain stem. From there the signals move through a series of parallel neural circuits that traverse various regions — from the brain stem to the midbrain and thalamus—and finish their journey at the auditory cortex. Together this complex circuitry analyzes and organizes our acoustic environment into a set of recognizable sounds, whether it be a familiar melody or the wail of a siren.
Kant's concepts of space and time were transcendental categories of human consciousness. The physical mechanisms of sensual cognition theoretically don't touch them at all.
But, on Kant's side, there is the possibility that physics could turn out to require the rejection of time as an objective condition. Philosopher Craig Callender writes (Is Time an Illusion? Scientific American 302:6 June 2010):
The equations of physics do not tell us which events are occurring right now — they are like a map without the “you are here” symbol. The present moment does not exist in them, and therefore neither does the flow of time. Additionally, Albert Einstein’s theories of relativity suggest not only that there is no single special present but also that all moments are equally real ... Fundamentally, the future is no more open than the past. [my emphasis]Quantum mechanics in seeking to describe quantum gravity has produced a real puzzle for physics:
Canonical quantum gravity emerged in the 1950s and 1960s, when physicists rewrote Einstein’s equations for gravity in the same form as the equations for electromagnetism, the idea being that the same techniques used to develop a quantum theory of electromagnetism could then be applied to gravity as well. When physicists John Wheeler and Bryce DeWitt attempted this procedure in the late 1960s, they arrived at a very strange result. The equation (dubbed the Wheeler-DeWitt equation) utterly lacked a time variable. The symbol t denoting time had simply vanished. [my emphasis in bold]Kant would presumably be pleased to hear that!
Physicists as yet haven't yet generally discarded the concept of time. But the problem remains unsolved. Still, Callender writes, "Physicists are able to compactly summarize the workings of the universe in terms of physical laws that play out in time. But this convenient fact should not trick us into thinking that time is a fundamental part of the world’s furniture." For more on this particular topic, see: Carlo Rovelli, Forget Time FQXi Community 08/25/2008.
Somewhere in the transcendental Beyond, Kant is chuckling at us.
(By the way, in explaining the above, Callender mentions another hitch in understanding the physics of time: "Austrian physicist Ludwig Boltzmann [1844-1906] ... reasoned that, because Newton’s laws work equally well going forward or backward in time, time has no built-in arrow." Physics is awesome.)
But surely our scientists can reassure us on the existence of space? They must have ruled out the possibility of Kant having the last laugh on that one, right? Well, maybe not.
George Musser removes that assurance from us in "Where Is Here?" Scientific American 313:5 Nov 2015. Einstein, it turns out, caused trouble there, too:
Although the shape shiftiness of spacetime explains away the kind of nonlocality that Newton talked about, it produces a new variety. It comes out of relativity theory's core innovation: that there's no such thing as a place outside spacetime, no external or absolute standard to judge it by. This seemingly self-evident proposition has remarkable consequences. It means that spacetime not only warps but also loses many of the qualities we associate with it, including the ability to define locations. ...Yeah, it looks like Kant is still in the game on space and time.
The ambiguity of localized measurements is a form of nonlocality. To begin with, quantities such as energy can't be situated in any specific place, for the simple reason that there is no such thing as a specific place. You can no sooner pin down a position than you can plant a flag on the sea. Points in space are indistinguishable and interchangeable. Because they lack any differentiating attributes, whatever the world consists of must not reside at points; space is unable to support any localized structure. Gravitational quantities must instead be holistic properties of spacetime in its entirety. [my emphasis]