From First Cause to Faithful Cause

A Tale of Logic, Beans, and the Credible Beliefs Between

What’s our best guess about why things are the way things are? Abduction—not kidnapping, not limb movement, but a form of reasoning—offers a new name for an old way through science, life, and faith. 

Logic has a reputation—not entirely unearned—as a dry, sterile, inflexible, and sometimes antagonistic corner of human thought. Despite all this, logic hosts more than the traps of contradictions and the cruel cudgels of fallacies; upon closer inspection, you’ll find an overgrown garden of flexible, speculative, and unruly species of thinking. Its modern history is full of stops and starts, paradoxes that pull rugs out from under towering intellectual giants, rendering them (and us all) sundry characters with egg on our faces (for example, a graphic novel about Frege, Russell, Wittgenstein, etc.). 

Reasoning is what we all do every day. Indeed trusted leaders encourage us, among all other possible verbs that do celestial work, to think. So let’s do it a bit better—but just a bit, for reasoning is no panacea, and it should help us discount, not make, overstrong claims. This essay, the first in a possible short series (other pieces in the series might touch on, say, the role of abduction in Bayesian probability, casualty, and the data sciences such as in The Book of Why), offers language meant to model and motivate better, more self-reflective inquiry equally at home in data sciences, Sunday school, and even the grocery store. (Fair warning: the boring bits about brown beans early in the next section offer a strict lesson meant to reward at the end.) 

One point of departure is an explosive aside in a recent book by Terryl and Nathaniel Givens, Into the Headwinds: “Religious faith may be posited as the best explanation to make sense of observable facts. Such reasoning, generally called abductive reasoning, is a rational process, though never fully conclusive.” While the Givenses bridge reason and religious faith, my interest here need not lean on sacred and profane distinctions; I claim that any reasoning that escapes the sterile bounds of hypotheticals to interact with messy lived experience also grounds itself in unverified premises whose adoption necessitates a leap of faith. All inquiry, upon closer reflection, begins underdetermined.  

This essay takes a broader point of departure (alongside this more technical essay), introducing abductive reasoning as new vocabulary for articulating an old practice common in science, religion, and everyday inquiry alike: we continuously generate probable explanations for why things are the way they are. Abductive reasoning gives us a name and some best practices for doing something we all do all the time. It helps us arrive at more faithful causes for why this world is the case.  

The Case of a Bag of Brown Beans

Let’s introduce abduction via its better-known neighboring analytic methods deduction and induction (the common root stems from the Latin verb ducere, or “to lead” in Latin: all three—deduction, induction, abduction—lead our thinking in different ways). A grocery story contains the world (check out these food essays and food scholarship resources by my colleague Emily Contois). Suppose you’re in a grocery store in a place that speaks a language you do not yet know and are searching for a bag of brown beans for your family’s chili recipe. Only the corners of the bean bags are see-through, and you can’t read the labels. So what do you do? 

You would most likely observe and reason (cf. lead) your way to a bag of beans. This process would surely be subconscious for mature minds, although we might imagine breaking down the process into its basic components so we could explain to a child how to navigate a store aisle alone for the first time: we have “these beans here,” “beans from a bag,” and “brown beans.” Next we work by reason and observation until we successfully merge these three into the happy conclusion, “These beans from this bag are brown beans.” 

So how might such reasoning work? Let’s try different ways to navigate the bean aisle.  

Deduction: to deduce your way to a bag of brown beans, you have to move from sure principle to particular. You begin with the sure principle that “all beans in this bag are brown.” You next observe the particular details of a bag of beans, noting that “these beans are from this bag.” From there, you deduce that “these beans are brown.” This is a sure sequence: given a true principle, deduce a solid conclusion from an observation. The problem, of course, is that to deduce, one must start from a true principle, and how is one to be sure of that except through non-deductive observation and speculation, like analogy and action at a distance? (Almost no one arrives at a grocery aisle already knowing where everything is. Even fewer people enter and exit this life with foundational principles in mind.) Each of us are born midstream, mid-cosmos, and as a result, our experiences of grocery aisles and everything else do not begin with many certain premises. As a regular shopper and former grocery stocker, I find many mysteries in grocery aisles—and, as we will see, abduction thrives on mysteries in need of explanations. 

Induction: inductive reasoning makes guesses by moving from particulars to probable principles. Say you find a (particular) bag of beans on a shelf: you start by observing some details about it such as “these beans are from that bag” and then observe a pattern in those details such as “these beans are brown.” From there, one could induce that “all beans in that bag are brown.” You might be right, but the guesswork here is obvious.

As David Hume and others in ancient India (whose modern-day chroniclers also include the second President of India) and Greece before him pointed out, induction relies on a circular assumption that the future will resemble the past, which is itself an inductive leap: it is probable but not certain. For example, you certainly hope that the results of your physics experiment won’t vary whether it takes place on Tuesday or Thursday this week, but only a fool insists that the tax auditor won’t care if you miss Wednesday’s deadline. Critics of induction insist that no one can be sure, before the fact, which corners of the cosmos are more like the tax auditor or the physics experiment. So induction usually gets the job done, but because of its circular guesswork, its insights do not always scale to general explanations: induction works best locally, or within reasonable limits and samples. For example, you can reasonably induce that since “these beans are from that bag” and “these beans are brown,” then “these beans from that bag are brown,” but you can’t reasonably induce anything from these observations about all other beans and bags. For example, “these beans are from this store” does not mean that “all beans from this store are brown.” Induction happens in strait gates and narrow ways.

We’ll review the strengths and weaknesses of deduction and induction in a moment, but now let’s come to the main event. 

Abductive reasoning is a bit different: it doesn’t make conclusions, proving like deduction or guessing like induction. As Charles Sanders Peirce (pronounced “Purse,“ and whose improbable life adventures are entertainingly narrated in The Metaphysical Club) coined, “abductive reasoning” helps generate explanations (or hypotheses) for the causes of observed phenomena. It is, Peirce claimed, “the only logical process which introduces a new idea.” (Data scientists, in a slightly different use of the word, talk about abduction as the way one arrives at an educated guess about how a theory explains an observation.) Abduction asks why, takes it all in, and then takes its best shot. 

Back in the grocery aisle, you can probably induce your way to a bag of brown beans, but as you do so, let’s say you stumble upon a puzzle in need of an explanation: you find a bag of beans spilled on the floor. Let‘s imagine you have never encountered a bag of spilled beans before, so what caused the spilled beans is, at least initially, a mystery to you. You start by observing locally (thanks induction!), “Hey, these beans on the floor are brown,” and then you might note “the beans in that bag next to the spilled beans appear brown too.” From here, you may now abduce an explanation: namely, “these beans on the floor are from the bag that spilled.” And therefore, you have a new premise from which to act: since spilled beans on a floor likely come from the nearby open bag, you can now believe that if you want brown beans for your chili, you should buy a bag of beans just like the bag that spilled brown beans. Instead of arriving at a conclusion (as deduction compels and induction guesses after), you’ve explained your way into a fresh premise. While deduction and induction lead you to the end, abduction leads you to a new start. The chain of reasoning here is so obvious, so everyday, that its work may be invisible at first glance. But the process gets you results: maybe you cleaned up a spill, and maybe you scored both a discount with the store manager and exited the store with the right bag of brown beans for your chili. But something else happened too: even though you have no direct knowledge and no sure principles, you, someone who has never encountered a spilled bean bag before, now boasts a new (to you) general hypothesis or explanation: “Beans spilled on floors next to an open bag of beans are probably from that bag.” You are now one hypothesis richer, however modest that hypothesis may be. Your explanation does not need to be perfectly true for you to now be free to test it. The old Russian proverb doverai, no proverai rhymes in a way the Reaganism does not: trust but verify. Abductive reasoning seeks for explanations without relying on local guesswork or waiting for perfect principles; what induction would frame as a probable conclusion, abduction takes as a hypothesis for testing. Abduction holds out conclusions with an open hand.  

As a method for generalizing faithful claims, abductive reasoning applies to far more than spilled brown beans in grocery aisles. For example, imagine you discover cracker crumbs and cheese crumbles on the shelf of your pantry. On the floorboards you also find a small hole disappearing into the innards of the walls. What hypothesis, explanation, or cause should you prioritize? Abduction instructs us to choose the most faithful cause that explains the most evidence with the fewest assumptions. In other words, most will abduce “a mouse did it“ because this is the cause most faithful in explaining the most evidence with the fewest improbable assumptions. This explanation is parsimonious. Theoretically, in preferring the mouse explanation, one is also implicitly and abductively weighing against other (and less probable) hypotheses. One could, in theory, also abduce other less and less likely explanations: in one, a family member left the mess and the unrelated hole has been there since construction; in another, you sleepwalked and had a messy midnight snack; or, in still another in which you slip into conspiracy, maybe alien spies are infiltrating your house, starting with planting false flags in the pantry, in a slow campaign to corrupt your mind. These hypotheses are not equally parsimonious: the mouse does the most work with the most probable assumptions. Simplex sigillum veri; simplicity is the seal of truth. Abduction doesn‘t compel one to solve the mystery—rather, like above, it sets up, sorts, and prioritizes explanations by their faithful causes to explain the evidence.  

To summarize for those who don’t mind a bit of formalism, let any situation involve at least three components, A, B, and C; in this case, let A = brown beans, B = these beans, and C = from that bag. So deduction proves by stringing together that A is B, and B is C, therefore A is C; Induction generalizes from A is C, taking A as a sample of B, and thereby concluding that B is (probably) C; and abduction explains why A is C, noting B is C, so hypothesizing A is (probably) B. See more technical details here (using MPS, not ABC). 

Abduction Beyond the Bag of Beans

“It’s elementary, my dear Watson!” Despite what we have been told (and his fictional website “The Science of Deduction” on the BBC show), Sherlock Holmes does not work by deduction; he doesn’t work entirely by induction either. Rather, Holmes works by abduction—and so do you and I. 

“You know my method,” said the great detective in The Adventures of the Speckled Band. “It is founded on the observation of trifles.” Deduction moves forward from principle to particular, but Sherlock, in his reasoning, moves backward from particular to probable explanation. Here it is worth making an important distinction. Holmes, whether in book or show, is making explanations, not conclusions. The conclusion (as in the narrative conclusion) is the first thing one knows in a detective narrative—the crime, the deed. (Deed, like the German Tat, puts the action in the past tense: a “deed” harkens back to the past tense “did.”) Mystery novels and crime shows start with the conclusion and then work backward to explain the action. (The last are made first.) What one needs is an explanation from a hidden cause for that deed, and so the detective, donning his deerstalker hat and not without some guile, sets out to reveal the probable cause for the deed and then only later, after swooning curiosity from his companions, explains his reasoning backward to that cause. Even though cause precedes effect in the event of the crime itself, the detective reasons in the other direction from effect to cause. He observes the results first, like fresh mud flecks on a left sleeve, to then abduce a probable explanation of that effect. Here, the sleeve bearer recently sat on the left of a cart pulled along mud-heavy roads. In the grocery aisle example, one abduces from the spilled beans effect back in time to the open bag cause. 

As with detective work, so with professional expertise. Consider the many ways professionals draw hidden past causes into the present: doctors diagnose (given these symptoms, which diagnosis is most likely?), family historians trace past stories with contemporary relevance, handymen often cover up blemishes by working backward to the causes (given these mistakes, which patch will do best?), psychologists recall their patients’ troublesome pasts into the present, teachers zero in on the (mis)understanding in their students’ minds in order to correct and guide them, chefs select among yesterday’s recipes with today’s ingredients in hand, editors hear and tighten what an author meant to write but didn’t, and the analyst formulates a pattern to explain past behavior. Many other examples could illustrate the fine art of finding causes faithful to the evidence at hand. Abductive reasoning is another name for how explanations can make sense of evidence in the present using the least extraordinary assumptions about causes in the past. Abduction, in other words, is elementary, intuitive, probable, conjectural, and born of observation—an activity of mind so normal it is often overlooked. 

Abductive reasoning twists backward in time. Time marches forward from cause to effects but we, like detectives in a plot, can only explain effects back to their causes. We make explanations pointed backward in time. If a pin pricks you, the pin is the cause of your pain, but you notice the pain before you notice the pin. So, even though cause precedes effect in the natural world, in our experience of the world, things are reversed: the observation of effect must precede the explanation of cause. A pin causes the pain, but we see the pin only after pain points to the pin as an explanation. “Ow! Why am I in pain? Oh, I see: this pin.” Thus we perceive the effect before its explanation. We don’t need to watch the rain to prove it gets the grass wet: we see the wet grass and abduce it must have rained. We see the case is B, and then conjecture a faithful cause for B: “If A were true, B would be obvious. B is the case. So, let us suspect A is true.” 

Faithful Causes and Abduction

We err if we imagine that faith and reason could ever proceed separately. Abductive reasoning seeks after faithful causes. What is the evidence for which faithful causes are the best explanation? Which explanations produce the best fruits, results, and effects, and for whom? Abduction sharpens such questions without forcing any particular answer: it reasons faithfully without dogmatism. Faith raises both big picture and everyday questions about how to live in pursuit of more faithful causes: what is the purpose of life? Why are we here on earth? What happens after death? What should one be doing here and now, and why? How does one answer such questions except by an act of abductive faith, or by reasoning the best evidence back to probable causes for the best possible effects? Other tools are welcome too, of course, but faith, if it is to have meaning, cannot be the mere machine-tight conclusions of deduction or only the probable guesswork of induction. The faithful cause questioning of abductive reasoning inspires the full court press of experimentation with all the tools one possesses—community, resources, inspiration, revelation, experience, and other forms of reasoning, etc.

While mileage may vary by observer, the case for pursuing faithful causes is clear to me: the material cosmos and the social communities we all inhabit are at once so profoundly beautiful, complex, and trying that I cannot deny that inquiry constitutes its own kind of faithful cause: the task of searching for more and more faithful causes is itself worthy of my reverence and effort. In turn, I honor and respect all who share an interest in the higher task of explaining and living so that our lives might lead to a world that works better. This faith requires that no one share my exact conclusions; rather it is a faith that invites us all to search for truths that work better together. What could be more faithful than building better understanding and a better world together?

In particular, I see an urgent need for better hypotheses for faithful causes that explain the abundant evidence of grace and growth, decay and suffering across the cosmos and every community I know. A crowning, convincing hypothesis for me, the one that does the best work, is that the cosmos performs and rewards a pattern of creative parents who—deeply embedded in a material cosmos far from abstract omnis—love, work, and weep for their children and other creations and thus welcome all to learn together from our own love, work, and weeping. I cannot deduce or only infer this; better, I abduce it as a faithful premise, whose consequences I weigh with an open hand. I grow as my understanding of our cosmological parentage molts and improves, since my knowledge evolves with many communities of interpretation. My hypothesis of humanity’s potential to serve a creative cosmos does real and necessarily imperfect work across many communities I belong to. Such faithful cause hypotheses explain with the fewest assumptions the most evidence I see to the best potential ends I know so far, although heaven knows it does not make everything better or even easier. How can we not cry out with joy and humility that the entire whole and every tittle of heaven and earth, already so abundant and complex, witness with Occam that entia non sunt multiplicanda praeter necessitatem (entities must not be multiplied beyond necessity)? Awed by the cosmos we inhabit, abduction bears experimental fruit with an open hand.  

Now mid-experiment, I see the value of faithful causes not merely in rearticulating their truth (except when useful to others) so much as trying to live as though faithful causes were true as one among larger communities that seek to experience, interpret, and build better faithful causes for all available evidence. So we direct our search for faithful causes to such communities of science, religion, literature, art, experience, and much else in the wisdom traditions. As a researcher and teacher, I often feel my career calling is not to influence others but rather to become optimally influenced by others’ best efforts at truth. A sacred part of that calling is acting while aware of how little I know: as conveniently on display in this essay, I usually find my understanding of things at best at a working minimum and my grasp of wisdom far below that. These welcomed limitations humble and discipline, guide and pardon my best but still fumbling efforts. They prompt me to learn from the best sources for explaining causes. They teach me to declare that if anything less would lead to better explanations that do better work, I, too, would follow that faithfully.    

A Minor-Key Manifesto for Thinking Abductively 

We all abduce: why not do so a bit more intentionally? Consider its case personified: abductive reasoning describes how folks parsimoniously justify explanations of the most evidence with the fewest extraordinary assumptions to the best ends. Explain the most while claiming the least. Underpromise and then overdeliver. It asks, which explanation does the most work with the least cost? It knows its limits. It yields daily decisions, justifies hypotheses for testing, treads calmly the white waters of incomplete information, delivers probable diagnoses, weighs evidence like experts, finds creativity in thought experiments, welcomes the strengths of induction and deduction, and knows it is often wrong enough to keep looking. In its self-conscious weakness lies the root of its reliable commitment to lasting inquiry. 

Abduction is no superhero. It is not triumphant. Its conclusions are never rock solid. Faithful action may never satisfy certainty seekers. It arrives in a minor key and stays for the swelling and falling cadenzas of our lives played out in experiment and adventure, heartbreak and grief, learning and wisdom. Abduction has no beef with rational inquiry; in fact it is the pathway to firmer premises for it. It formulates hypotheses for scientific testing (hypothesis formulation precedes the scientific method) and yet its self-reflective humility permits no dogmatism, including rationalism, scientism, and other doctrinaire orthodoxies. It claims no discoveries as its own, offering instead flashlights in the moonlit valleys of faithful action. It and deduction work hand in hand, the first bringing interrelated hypotheses and the second filling in the gaps. Like induction, it hopes to be pliant, versatile, tolerant, and non-possessive of its own mode, even as it gives a tool for understanding causes and explanations, not consequences and conclusions. It cares deeply about evidence, even all the evidence (not just this or that discipline, not just the convenient bits, and not just the contrarian bits, but like a sociable Holmes, remains open to an evolving sociomaterial world). It is calm and alert in the face of uncertainty and mystery. It is humble enough that it regularly seeks to revise its view even as it also encourages rigorous explanations that might have far-reaching consequences beyond the sample size at hand. It knows it will never arrive at a truth worth keeping entirely on its own: rather it seeks to begin better by seeking to paint pictures with shared palettes of evidence, experimentation, insight, and revelation. 

We may bear moving witnesses of our personal truths from the podiums of everyday life. But “my personal truth,” while a dignifiable start, is never an end for abductive reasoning: it nudges us to share our evidence of truth, our witnesses, so that we in our communities may weigh, sort out, dignify, interpret, and discern a better balance of truths wherever they may be found. Abduction raises and widens the stakes of inquiry, prying open consideration of a broader set of sources while also collectively experimenting on the resulting explanations in search of parsimony. No singular source is sufficient. No witness stands alone. No truth could ever be mine alone.

An omnivore on a diet, abduction is no excuse to let any influence, no matter how comfortable or convenient (or shocking or reactionary) justify my prior or favored thoughts. Open to any pupil’s evidence and arguments, it remains the stringent schoolmaster: it invites the overconfident to pause, without panic or passion, to reassess the causes for their convictions. It bends to curiosity and stands unmoved by zealotry, asking throughout, what evidence do we value and why? What explanations do we treasure and why? In seeking to understand the work that explanations do and how that work might be improved, it asks, What is the evidence for the best explanations that lead to the best ends? 

Readers here—or those with ears to hear already conversant with faith traditions built on many holy books, an open canon, and ongoing inspiration—will have by now intuited that much of this minor-key manifesto to abductive reasoning doubles as an open allusion and thinly veiled love letter to the restored faith tradition of, among other modern religions, scientific inquiry (in the older sense of the science as Wissenschaft, or “knowledgeship”). Scientific inquiry is baked into the modern restoration of all things too; scientific inquiry too takes faith in its questions because it, like faith, must seek out the best causes. So too is seeking for faithful causes abductively another name for the pursuit of science, broadly taken. 

Unlike deduction, abduction speculates. Unlike induction, abduction asks why and scales its samples. It formulates questions. It gives us language to consider how to lift and better learn the standards by which to seek to explain evidence and then translate those explanations into shots at truths. Abduction observes. It reasons. It explains. It adjusts. It experiments. It aims and tries again. It accommodates differences and seeks patterns. It expands our understanding, humbles us when we don’t understand, and reveals more truth when we learn to understand together. It is at once everyday and cosmological in its calls for all to discover and live enduring truth more fully. Abductive reasoning suits latter-day faith, science, and everyday inquiry just fine. 

On balance, perhaps that’s not such a bad bag for holding and sometimes spilling the beans.  

Benjamin Peters is a Wayfare Associate Editor. He is also a media scholar, author, and editor interested in Soviet century causes and consequences of the Information Age.