Epistemological Metaphors Part 2

Peirce’s Cable, Quine’s Web, and Neurath’s Boat 
Descartes was inspired by Euclid’s geometric proofs, which demonstrated their claims to truth through incremental steps each with a simple justification in a long chain of reasoning. He likened himself to an architect needing “to demolish everything completely and start again right from the foundations,” and he sought then to build an edifice of knowledge upon such metaphysical first principles using Euclidean chains of reasoning. 

Letting the “foundation” metaphor alone for now, Peirce pointed out a key problem with the chain metaphor for knowledge. If Descartes had come up with a “long chain of reasoning” which could, by its end convince us that, say, making a cup of coffee is what we ought to do about now, that conclusion would be as weak as the weakest link of reasoning that aided in the construction of the chain. Even with a rock solid foundation on which to base our beliefs, in Descartes architectural model for knowledge, the strength of our foundation is no more important than the strength of each individual link in a chain of reasoning. Rather than model philosophy on mathematics, Peirce recommended that,

“Philosophy ought to imitate the successful sciences in its methods, so far as to proceed only from tangible premises which can be subjected to careful scrutiny, and to trust rather to the multitude and variety of its arguments than to the conclusiveness of any one. Its reasoning should not form a chain which is no stronger than its weakest link, but a cable whose fibers may be ever so slender, provided they are sufficiently numerous and intimately connected.”

Even better than having one convincing line of thought that leads to a conclusion is the possibility of generating multiple such lines of reasoning to support it. What is emphasized in Peirce’s cable metaphor is the importance of all the inferential connections between fibers or beliefs that don’t necessarily all follow in a single sequence of deductions but rather wrap around one another in mutual support.

    

The problem with Descartes’ chain metaphor is that the strength of the chain fails as easily as a single link can break. And we know that they can break since we’ve all made deductions that we thought were rock solid in the past but were later shown to have serious flaws. Quite heavy links may be found to weigh on the support of a single loop of hair, while a cable can endure the failure of a few fibers so long as there are enough other fibers remaining. It is the interconnectivity of propositions rather than a single sequence of deductions that makes a cable of beliefs strong.

Peirce’s cable could be seen as a hemp rope where no single fiber could extend along the entire length, yet, pulling as hard as we might, it won’t come apart. No single belief imagined as a fiber in such a cable or rope is any more a core or foundational belief without which the whole structure would collapse. W. V. O. Quine saw this sort of interconnectedness and mutual support for our systems of belief as a web. Perhaps we can even mix metaphors and think of the structure of our beliefs as a web of ropes or cables rather than a web of distinct fibers. In any case, we can imagine reweaving parts of such a web while the greater structure remains intact. With enough reweaving, it is possible to imagine that after a time the entire web no longer has any of the same fibers as it did before. It could in principle be completely rewoven without needing a “doubt everything” clearing away of all past knowledge; yet, at no time would the majority of beliefs in the web have gone unsupported by other strands. Our existing beliefs are all the foundation we need to extend and improve our webs of belief without any limits on the degree to which our beliefs could be improved.

While cables, ropes, and webs are excellent antidotes to chains and the myth of core beliefs, my favorite antidote to foundationalism—the thought that we need a rock solid foundation to claim any knowledge which often takes the form of a Platonic essence—is Neurath’s boat. While Descartes modeled his philosophical method on mathematics, following Peirce, Otto Neurath also took science to be the proper model for philosophical thinking. As Quine explained, rather than clearing away all but a single bedrock belief or two upon which to build a system of thought,

"Neurath has likened science to a boat which, if we are to rebuild it, we must rebuild plank by plank while staying afloat in it. The philosopher and the scientist are in the same boat. Our boat stays afloat because at each alteration we keep the bulk of it intact as a going concern."

It doesn’t merely stay afloat. In fact, as contemporary philosopher of religion and self-described pragmatist Jefferey Stout put it, Neurath’s boat

“can travel the open seas, trade with foreign places, and send parties in search of virgin timber. Its crew can take unimagined treasures on board, plunder shipwrecks for usable gear, and invent an engine to pull weight once pulled by oar.”

Presumably at that point, we could ditch the oars. Note that there is no analogue to doing so in the chain metaphor. Every link is integral to a line of reasoning, whereas in attaining greater understanding of, say, the atom, it may be useful at some point in our educations to think of it as a round particle and later to drop that notion in favor of the Rutherford-Bohr “planetary” model, later a cloud model, and later still some better not yet imagined conception that we perhaps could have never created without such scaffolding. What this ship cannot do is sail into dry dock for a complete overhaul. In Neurath’s words,

"We are like sailors who on the open sea must reconstruct their ship but are never able to start afresh from the bottom. Where a beam is taken away a new one must at once be put there, and for this the rest of the ship is used as support. In this way, by using the old beams and driftwood the ship can be shaped entirely anew, but only by gradual reconstruction."

Just as the web of beliefs can be rewoven, the ship can be rebuilt, but we can only do it from aboard the ship. Such is the human condition. This rebuilding is the process of criticizing and revising our beliefs. While we can’t call all of our beliefs into question at once—where would we stand to do that?—there is no belief we have that cannot be subjected to such criticism. The complete overhaul (question everything!) of knowledge that Descartes wanted to do is not possible in this analogy, and it isn’t possible in practice either. Though many people hoped at one time that all our knowledge could be erected as a tower on top of solid ground, such a model does not agree with how knowledge functions in practice. And just what is it, a pragmatist wonders, that we wanted to be able to do in that tower that can’t be done in Neurath’s boat?

Peirce’s Cable, Quine’s Web, and Neurath’s Boat are metaphors better suited to how knowledge acquisition functions than are Descartes’ foundation and chain metaphors. The position that Descartes imagined himself to be in deducing his existence was never the position we were actually in. We always already have beliefs. What we need to do is decide which ones to keep, which ones to drop, which ones to change, and which ones to add in an ongoing process that seems very little indeed like clearing a plot of land to erect a building from the ground up. There is no single belief such that if it needed to be updated in light of new experience it would cause the entire tower of knowledge to collapse. The reweaving of a web or the repairs and alterations on a boat while at sea seem much more to the point.