[This was a reflection paper I submitted for my class 24.01 Classics of Western Philosophy. I make references to terms in the class (e.g. Copy Principle, impressions, Doctrine of Recollection, etc.) that I didn’t explain here because my intended reader (course staff) already knew about them. I may or may not change that soon.]
It was twelve degrees–not above, but below zero–in Rapid City, South Dakota. That this temperature was meant for frozen German sausages and not Filipino astrophysicists-in-training did not faze me: I unpacked my camera, donned four layers of clothing, and set out for a night of observing.
I marveled at the stars, inspired that we could gain so much knowledge about them despite their being light-years away. But although I was excited by what I could see, I was exponentially more intrigued by what I could not. Lurking in the blackness between the pinpricks of light is a mysterious substance called dark matter; and even after decades of research, no one knows exactly what it is.
In the 1930s, Dutch astronomer Fritz Zwicky measured the total mass of the galaxies in the Coma Cluster using two methods: first by estimating it from all the visible matter and second by estimating it from their velocities. Interestingly, he found that the latter method returned a number two hundred times the former–an alarming disagreement.
Could there be a large mass of invisible matter responsible for this difference, perhaps some “dunkle Materie” (literally “dark matter”)? His idea did not receive mainstream acceptance until the 1970s when Vera Rubin, an American astronomer, observed a similar mass discrepancy in individual galaxies. There was simply more mass than we could see.
After extending this investigation into other galaxies, clusters, and the structure of the cosmos as a whole, it turns out that dark matter is disturbingly ubiquitous. Now, we believe that all of the universe’s matter content is composed of 15% normal matter and 85% dark matter. Until now, we know nothing about it for sure other than it’s there. Our collective ignorance is as humbling as it is exciting; it drives the active search for this object using theory, ever more advanced telescopes, particle accelerators, and underground detectors.
But let us take a step back and ask a more foundational question. If we know nothing about dark matter, how are we even able to mount a search for it? If some god commanded me to look for a krambowampuk–a divine invention about which no one knows anything–I would not even know where to start.
This question is reminiscent of one that Plato raised in Meno (80d-e). “How will you look for [virtue], Socrates, when you do not know at all what it is?” Meno asks. “If you should meet with it, how will you know that this is the thing that you did not know?” This is the Paradox of Inquiry: we cannot search for something we know because we already know it; but we likewise cannot search for something we do not know because we would not know when we do find it. What then can we actually search for?
Plato resolves this paradox using the Doctrine of Recollection. I argue, however, that this resolution is unnecessary (besides being non-empirical) because the paradox is not even a paradox at all. Indeed, we cannot search for things that we totally know or do not know. But Plato crucially misses the fact that we can know things partially–in fact, this is the only extent to which we can ever know anything–and partial knowledge of X is what we can use to search for a more complete understanding of X.
Meno is mistaken in thinking that Socrates knows nothing about virtue. The mere fact that they have a word for it, that they have vague ideas about its qualities, that they can engage in debate about it suggests that they do have partial knowledge. This partial knowledge should then seed their search, beginning the accumulation of yet more knowledge until they discover a definition of virtue that satisfactorily unifies all knowledge acquired thus far.
This is analogous to the case of dark matter. Although we are clueless about what it is, we have a clearer idea about what it is not. We know that it cannot interact with electromagnetic radiation, that it cannot be beyond a certain range of energies, that it cannot be matter as we know it, and so on. Using these constraints, we continuously tighten our search parameters until we finally find the specific object or phenomenon that fits all constraints and accounts for the mass discrepancy.
Now, one might object that this only sets the problem back. Yes, we can search for X given partial knowledge about it; but how do we even acquire partial knowledge in the first place? While Plato might unsuccessfully attempt to resolve this yet again using the Doctrine of Recollection, I take the empiricist position that we gain partial knowledge exclusively through experience.
To illustrate, let us take a first premise consistent with Hume’s Copy Principle. We gain new knowledge in only two ways: by integrating new sense data into our knowledge base or by creating a unique permutation of existing impressions and/or ideas. For the second premise, suppose we have a blind person who does not have a single idea about color. Nothing in his knowledge base bears even a remote connection with the idea of color.
With these premises, we can conclude that color for him would be inconceivable through thought alone. The only way he could learn it would be through new input from experience. And when this happens, the experience would be abrupt, forceful, and sharp. Overall, these two ideas, of partial knowledge and of the role of experience in gaining partial knowledge, resolve the Paradox of Inquiry without resorting to non-empirical proposals.
In the case of dark matter, the simplistic analog to the blind man’s seeing color would be Zwicky’s and Rubin’s discovery of the mass discrepancy. Because of its novelty and detail, no one could have imagined the problem’s elaborate existence using pure thought. Their observations became incorporated into our collective knowledge base simply as new information.
Then, upon further analysis of the data, they found that the missing mass problem is actually part of an even larger mystery. At this point, their novel information then transforms into partial knowledge that launches the enterprise of illuminating an even grander kind of unknown. To answer Meno, this is how we search for the unknown.
That night in the frigid outdoors, I was enveloped in a sky full of darkness in both the literal and figurative sense of the word. As I stared at the sky, the darkness stared back, taunting me with its mystery. Nevertheless, I rest inspired, knowing that we–as insignificant as we are–are able to uncover little by little, ever more knowledge about our universe. Using thought and observation, we launch ourselves into an intrepid journey to illuminate the dark. And although it sounds daunting, it is a hundredfold more exciting.