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Absolute Certainty
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Prompt 1: Provide an full elaboration on Cromwell’s Rule defined below
Cromwell's Rule: why absolute certainty almost never belongs in the model
Read the section by contrast: Cromwell’s Rule: An Elaboration as a load-bearing piece, Understanding Cromwell’s Rule as a load-bearing piece, and Examples as a test case. Each part is there for a reason, and the reader should be able to say what gets lost if those distinctions collapse together.
In plain terms: Cromwell’s Rule, named after the English statesman Oliver Cromwell and introduced by statistician Dennis Lindley, is a principle in Bayesian statistics.
Keep Cromwell’s Rule: An Elaboration distinct from Understanding Cromwell’s Rule. They are not interchangeable bits of vocabulary; they point the reader toward different judgments, objections, or next steps.
A quick way to test the page is to imagine an ordinary disagreement in which Cromwell’s Rule matters. What would a careful reader now say, test, or withhold because Cromwell’s Rule: An Elaboration and Understanding Cromwell’s Rule has been made clearer? If the page cannot answer that, it still needs more contact with life.
The first move should give the reader something firm to hold. Then the later prompts can deepen the issue instead of circling it.
A fair pushback is that ordinary life cannot wait for perfect evidence. That is true, but it does not give favored beliefs a free pass. The section should show how acting under uncertainty differs from excusing weak support.
Treat Cromwell’s Rule: An Elaboration, Hypothetical Discussion on Cromwell’s Rule, and Resources on Cromwell’s Rule as handles, not slogans. The question should remain open enough for revision but structured enough that disagreement is not mere drift. The practical habit to learn is calibration: matching confidence to evidence rather than to comfort, repetition, or social pressure.
“ Cromwell’s rule, named by statistician Dennis Lindley, states that the use of prior probabilities of 1 (“the event will definitely occur”) or 0 (“the event will definitely not occur”) should be avoided, except when applied to statements that are logically true or false, such as 2 + 2 equaling 4.”
These are the probabilities assigned to events before observing any new data. They reflect our initial state of belief or knowledge.
This is the process of adjusting our prior probabilities based on new evidence to obtain posterior probabilities.
If a prior probability is set to 0 or 1, no amount of new evidence can change this belief. This goes against the fundamental Bayesian principle of updating beliefs with evidence.
In the real world, few events are absolutely certain or impossible. Allowing for some degree of uncertainty (i.e., probabilities between 0 and 1) is more practical and realistic.
The only exceptions to this rule are statements that are logically true or false (e.g., mathematical truths like 2 + 2 = 4).
By avoiding 0 or 1, we remain open to updating our beliefs in light of new evidence, fostering a more flexible and adaptive mindset.
This rule helps prevent dogmatic thinking, where beliefs are held rigidly regardless of contrary evidence.
It promotes rational decision-making by ensuring that our beliefs can be modified based on evidence, which is central to Bayesian reasoning.
Scientists often adopt Cromwell’s Rule to maintain an open-minded approach to hypotheses, allowing them to be updated or discarded based on experimental data.
In fields like finance and engineering, where decisions are based on probabilistic models, avoiding absolute priors helps in making more robust and adaptable predictions.
In decision-making processes, especially under uncertainty, this rule ensures that decisions remain flexible and responsive to new information.
Suppose a scientist is testing a new hypothesis. Assigning a prior probability of 0 to the hypothesis would mean they are certain it is false, regardless of any evidence that may arise. By assigning a prior probability slightly above 0, the scientist remains open to considering evidence that might support the hypothesis.
In a medical context, if a doctor assigned a prior probability of 0 to a rare disease for a patient, no amount of symptoms or test results suggesting the disease could change the diagnosis. By assigning a low but non-zero prior probability, the doctor stays open to adjusting the diagnosis based on new information.
Our knowledge about the world is often incomplete. New evidence or data can emerge, changing the likelihood of an event. Assigning a 0 probability excludes the possibility of encountering such evidence entirely.
By using probabilities between 0 and 1, we allow the data we collect to have a greater influence on our final conclusions (posterior probabilities). This leads to more flexible and adaptable inferences.
The rule makes an exception for statements that are logically true or false, such as mathematical identities (e.g., 2 + 2 = 4) or logical tautologies (e.g., “If it is raining, then it is raining”). In these cases, it is appropriate to assign a prior probability of 1 or 0, respectively, because the truth or falsity of the statement is known with absolute certainty.
Cromwell’s Rule is particularly relevant in the context of Bayesian inference, where prior probabilities are combined with likelihood functions to calculate posterior probabilities. If a prior probability of 0 or 1 is used, it can lead to inappropriate or misleading conclusions, as the posterior probability will always be 0 or 1, regardless of the evidence.
- Cromwell’s Rule: An Elaboration: Cromwell’s Rule, named after the English statesman Oliver Cromwell and introduced by statistician Dennis Lindley, is a principle in Bayesian statistics.
- Understanding Cromwell’s Rule: In Bayesian statistics, prior probabilities represent our initial beliefs about the likelihood of events before considering new evidence.
- Examples: Cromwell’s Rule is a critical principle in Bayesian statistics, emphasizing the importance of keeping prior probabilities between 0 and 1 unless dealing with logically certain statements.
- Belief calibration: Cromwell’s Rule concerns how strongly the available evidence warrants belief, disbelief, or suspension of judgment.
- Evidence standard: Support, counterevidence, and merely persuasive appearances have to be kept distinct.
Prompt 2: Elaborate on how an absolute credence of 0 or 1 entails epistemic blindness.
The real issue is what The Role of Credence in Epistemic Processes changes once it becomes precise.
Read the section by contrast: The Role of Credence in Epistemic Processes as a load-bearing piece and Examples Illustrating Epistemic Blindness as a test case. Each part is there for a reason, and the reader should be able to say what gets lost if those distinctions collapse together.
In plain terms: Epistemic blindness refers to the inability or unwillingness to revise one’s beliefs in the face of new evidence.
Keep The Role of Credence in Epistemic Processes distinct from Examples Illustrating Epistemic Blindness. They are not interchangeable bits of vocabulary; they point the reader toward different judgments, objections, or next steps.
A quick way to test the page is to imagine an ordinary disagreement in which Cromwell’s Rule matters. What would a careful reader now say, test, or withhold because The Role of Credence in Epistemic Processes and Examples Illustrating Epistemic Blindness has been made clearer? If the page cannot answer that, it still needs more contact with life.
This middle step keeps the thread moving. It carries the pressure already on the table toward the next distinction instead of letting the page break into separate mini-essays.
A fair pushback is that ordinary life cannot wait for perfect evidence. That is true, but it does not give favored beliefs a free pass. The section should show how acting under uncertainty differs from excusing weak support.
The deeper issue in Cromwell’s Rule is usually calibration, not a melodrama between certainty and skepticism. That turns the central distinction into a question about the right degree of confidence before it hardens into a slogan.
This section should give the reader a usable epistemic lever: what would support the central claim, what would count against it, and what would make suspension of judgment more rational than either assent or denial. The point is not to make Cromwell’s Rule tidy; it is to help the reader notice the difference between having a belief, having a reason, and having enough reason.
For a companion resource on calibration, credence, and structured rational judgment, see Credencing.com.
Epistemic blindness is a state where one is unable to see or consider alternative possibilities due to rigid belief structures.
This rigidity can lead to a failure to recognize new information, resulting in a static and potentially flawed understanding of the world.
A credence between 0 and 1 indicates a belief that is open to revision based on new evidence.
A credence of exactly 0 or 1 signifies absolute certainty or impossibility, leaving no room for change.
Bayesian Updating: Bayesian reasoning relies on updating our beliefs in light of new evidence. If we start with a credence of 0 or 1, our belief system becomes impervious to change, as no amount of evidence can alter these extreme probabilities. Learning from Evidence: When we assign a non-absolute credence, we acknowledge that our current understanding may be incomplete or flawed, and we remain open to learning from new evidence.
Bayesian reasoning relies on updating our beliefs in light of new evidence. If we start with a credence of 0 or 1, our belief system becomes impervious to change, as no amount of evidence can alter these extreme probabilities.
When we assign a non-absolute credence, we acknowledge that our current understanding may be incomplete or flawed, and we remain open to learning from new evidence.
Resisting Change: Absolute credence fosters dogmatism, where beliefs are held rigidly despite contradictory evidence. This resistance to change can lead to outdated or incorrect views. Closed-mindedness: By refusing to consider alternative possibilities, individuals with absolute credence can become closed-minded, dismissing new information that could refine or correct their beliefs.
Absolute credence fosters dogmatism, where beliefs are held rigidly despite contradictory evidence. This resistance to change can lead to outdated or incorrect views.
By refusing to consider alternative possibilities, individuals with absolute credence can become closed-minded, dismissing new information that could refine or correct their beliefs.
Rationality and Evidence: Rational decision-making involves weighing evidence and updating beliefs accordingly. Absolute credence undermines this process by precluding any consideration of new or conflicting evidence. Error in Judgment: Decisions based on absolute credence can be flawed, as they ignore the probabilistic nature of most real-world events and the potential for error in our initial assessments.
Rational decision-making involves weighing evidence and updating beliefs accordingly. Absolute credence undermines this process by precluding any consideration of new or conflicting evidence.
Decisions based on absolute credence can be flawed, as they ignore the probabilistic nature of most real-world events and the potential for error in our initial assessments.
Hypothesis Testing: Scientists often begin with hypotheses that have non-absolute credence. This openness allows them to update their hypotheses based on experimental results. An absolute credence of 0 in a hypothesis would mean no evidence, however compelling, could ever support it. Scientific Progress: Scientific advancements depend on the ability to revise theories. Epistemic blindness resulting from absolute credence stifles this progress.
Scientists often begin with hypotheses that have non-absolute credence. This openness allows them to update their hypotheses based on experimental results. An absolute credence of 0 in a hypothesis would mean no evidence, however compelling, could ever support it.
Scientific advancements depend on the ability to revise theories. Epistemic blindness resulting from absolute credence stifles this progress.
Diagnostic Flexibility: Doctors must remain open to revising diagnoses based on patient symptoms and test results. Assigning a prior probability of 0 to a rare disease can lead to misdiagnosis, as no amount of evidence will prompt the doctor to consider that disease. Patient Outcomes: Flexible credence ensures better patient outcomes by allowing doctors to consider and incorporate new evidence into their diagnoses.
Doctors must remain open to revising diagnoses based on patient symptoms and test results. Assigning a prior probability of 0 to a rare disease can lead to misdiagnosis, as no amount of evidence will prompt the doctor to consider that disease.
- The Role of Credence in Epistemic Processes: Credence refers to the degree of belief or probability that we assign to a proposition.
- Examples Illustrating Epistemic Blindness: Assigning an absolute credence of 0 or 1 to any proposition leads to epistemic blindness by rendering our belief systems inflexible and closed to new evidence.
- Borderline case: The reader should be able to say what would make the claim merely plausible rather than justified.
- Objection test: A strong section names the best reason a careful critic would withhold assent.
- Calibration test: The answer should distinguish certainty, high confidence, tentative belief, and responsible agnosticism.
Prompt 3: Create a hypothetical discussion between an epistemologist who has just introduced Cromwell’s Rule and a student who feels the absolute credences of 0 or 1 are sometimes justified.
The real issue is what Epistemologist changes once it becomes precise.
Keep Epistemologist and Student in the same frame. Each piece is doing a different job, and the page gets muddy if the reader cannot say what is being identified, what is being tested, and what would change if one piece disappeared.
In plain terms: “Today, I’d like to introduce you to Cromwell’s Rule. This principle, named after Oliver Cromwell, suggests that in probabilistic reasoning, we should never assign a probability of 0 or 1 to any event unless it is logically impossible or a certain truth, respectively. This is.
Keep Epistemologist distinct from Student. They are not interchangeable bits of vocabulary; they point the reader toward different judgments, objections, or next steps.
This middle step keeps the thread moving. It carries the pressure already on the table toward the next distinction instead of letting the page break into separate mini-essays.
Treat Cromwell’s Rule: An Elaboration, Hypothetical Discussion on Cromwell’s Rule, and Resources on Cromwell’s Rule as handles, not slogans. The question should remain open enough for revision but structured enough that disagreement is not mere drift. The practical habit to learn is calibration: matching confidence to evidence rather than to comfort, repetition, or social pressure.
This section should give the reader a usable epistemic lever: what would support the central claim, what would count against it, and what would make suspension of judgment more rational than either assent or denial. The point is not to make Cromwell’s Rule tidy; it is to help the reader notice the difference between having a belief, having a reason, and having enough reason.
So, as we discussed, Cromwell’s Rule advises against assigning absolute probabilities of 0 or 1 unless dealing with logical truths. Does this resonate with everyone?
Professor, I understand the value of considering uncertainty, but there are cases where absolute certainty seems justified. Isn’t it perfectly reasonable to assign a 1 probability to the statement “I am currently sitting in this chair?”
That’s an interesting point. Tell me more about why you think so.
Well, I can feel the chair beneath me, and I’m actively perceiving the classroom. To deny this absolute certainty feels illogical.
That’s a common intuition. But have you considered the possibility of being deceived? Perhaps it’s an elaborate dream or a simulated reality. While highly unlikely, we can’t definitively rule it out.
But that’s just a philosophical thought experiment, right? In the real world, such possibilities are negligible.
True, but the point is that absolute certainty requires complete knowledge, which we seldom possess. Cromwell’s Rule encourages acknowledging this limitation. Even in your chair example, there’s a tiny sliver of uncertainty, however improbable.
I see your point, but assigning a very high probability, close to 1, achieves the same outcome for most purposes, doesn’t it?
It can seem that way. But there’s a subtle difference. When you assign a 0.99 probability instead of 1, you leave a sliver of space for new information. Imagine if, say, tomorrow you woke up with amnesia. You wouldn’t be certain about anything, including whether you sat in that chair yesterday.
Okay, that’s a fair point. But couldn’t Cromwell’s Rule make assigning probabilities overly complicated? Isn’t it sometimes simpler to say something is certain or impossible?
Simplicity can be appealing, but it can also be misleading. Cromwell’s Rule encourages a more nuanced approach. It highlights the fact that most knowledge falls on a spectrum of likelihood, not absolute categories.
I suppose I can see the value in that, especially for scientific inquiry where new evidence is constantly emerging.
Exactly! By avoiding absolute credences, we stay open to revising our beliefs as we learn more. It’s a more robust and adaptable way of approaching knowledge.
Today we’ll discuss Cromwell’s Rule, which advises against assigning prior probabilities of exactly 0 or 1, except for logically true or false statements.
But surely there are some cases where it makes sense to have an absolute credence of 0 or 1? What if I’m absolutely certain about something?
Even if you feel absolutely certain, assigning a probability of 0 or 1 represents a state of complete dismissal or complete commitment that precludes any possibility of revising your belief based on new evidence.
But if I know something with 100% certainty, like the fact that I exist, doesn’t that justify a probability of 1?
The problem is that very few propositions outside of logical tautologies or mathematical identities can be known with 100% certainty. There is always some degree of uncertainty in most real-world situations.
- Epistemologist: “Today, I’d like to introduce you to Cromwell’s Rule. This principle, named after Oliver Cromwell, suggests that in probabilistic reasoning, we should never assign a probability of 0 or 1 to any event unless it is logically impossible or a certain truth, respectively. This is.
- Student: “I understand the general idea, but aren’t there situations where assigning an absolute credence of 0 or 1 is actually justified? For example, if I see a fair coin flip result in heads, can’t I assign a probability of 1 to the proposition ‘The coin landed heads’?”
- Epistemologist: “That’s a good point, and it’s important to consider the context of observation. However, even in that scenario, Cromwell’s Rule would encourage you to think about the reliability of your observation. Could there have been an error in your perception? Is it possible, however.
- Student: “But what about mathematical truths? If I say ‘2 + 2 = 4’, isn’t it completely justified to assign a credence of 1 to this statement?”
- Epistemologist: “Yes, mathematical truths are an exception because they are tautological and based on logical certainty. Cromwell’s Rule is more applicable to empirical and contingent propositions where there is room for doubt due to the limitations of our knowledge and potential for new.
- Student: “I see. So, Cromwell’s Rule is more about maintaining a stance of epistemic humility in the face of empirical uncertainty. But doesn’t this make decision-making difficult if we always entertain the possibility of being wrong?”
Prompt 4: What resources related to Cromwell’s Rule are available?
The real issue is what Books changes once it becomes precise.
Keep Books, Articles and Papers, and Online Resources in the same frame. Each piece is doing a different job, and the page gets muddy if the reader cannot say what is being identified, what is being tested, and what would change if one piece disappeared.
In plain terms: “The Logic of Scientific Discovery” by Karl Popper While not exclusively about Cromwell’s Rule, Popper’s philosophy of science emphasizes the importance of falsifiability and the tentativeness of scientific knowledge, which aligns well with the principles behind Cromwell’s Rule.
Keep Books distinct from Articles and Papers. They are not interchangeable bits of vocabulary; they point the reader toward different judgments, objections, or next steps.
A quick way to test the page is to imagine an ordinary disagreement in which Cromwell’s Rule matters. What would a careful reader now say, test, or withhold because Books and Articles and Papers has been made clearer? If the page cannot answer that, it still needs more contact with life.
By this point the clearing work should already be done. The last move should gather the earlier distinctions into a judgment the reader can actually use.
A fair pushback is that ordinary life cannot wait for perfect evidence. That is true, but it does not give favored beliefs a free pass. The section should show how acting under uncertainty differs from excusing weak support.
One honest test after reading is whether the reader can use Cromwell’s Rule: An Elaboration to sort a live borderline case or answer a serious objection about Cromwell’s Rule. The answer should leave the reader with a concrete test, contrast, or objection to carry into the next case. That keeps the page tied to what would make a belief worth holding, revising, or abandoning rather than leaving it as a detached summary.
The Logic of Science” by E.T. Jaynes This book covers Bayesian probability theory extensively and discusses why assigning probabilities of 0 or 1 can be problematic in the context of scientific reasoning.
Probability This entry provides a comprehensive overview of probability theory, including discussions on Bayesian probability, which is closely related to Cromwell’s Rule.
Cromwell’s Rule An accessible article that explains Cromwell’s Rule in the context of rationality and decision-making, suitable for readers who are new to the concept.
Probability and Statistics While not specific to Cromwell’s Rule, Khan Academy offers foundational courses on probability and statistics, which can help understand the broader principles related to probabilistic reasoning.
Introduction to Bayesian Inference There are numerous videos explaining Bayesian inference, which often discuss why probabilities should not be absolute and how Cromwell’s Rule fits into this framework.
Bayesian Statistics: From Concept to Data Analysis This course provides a deeper dive into Bayesian statistics, where Cromwell’s Rule is relevant in avoiding absolute credences.
The Power of Believing That You Can Improve by Carol Dweck Although not directly about Cromwell’s Rule, this talk on growth mindset aligns with the idea of remaining open to new evidence and adjusting beliefs accordingly.
While there might not be a plethora of articles specifically on Cromwell’s Rule itself (given it’s a principle within a broader field), you can find discussions of it in statistics and decision analysis journals. Look for articles that mention “prior probabilities” or “Bayesian reasoning.” Here’s a starting point, but using academic search engines like JSTOR or Google Scholar might yield more results: [scholarly article on cromwell’s rule]
Many statistics textbooks discuss Bayesian reasoning and assigning probabilities. These sections might mention Cromwell’s Rule as a best practice. Try searching for textbooks with titles like “Introduction to Bayesian Statistics” or “Decision Theory.”
Several websites explain Cromwell’s Rule in a clear and concise way. Here are a couple of examples: DeepAI: [Cromwell’s Rule definition ON DeepAI deepai.org] Wikipedia (though brief): [Cromwell’s rule Wikipedia en.wikipedia.org]
[Cromwell’s Rule definition ON DeepAI deepai.org]
[Cromwell’s rule Wikipedia en.wikipedia.org]
The statistician who named Cromwell’s Rule is Dennis Lindley. While finding resources directly on Cromwell’s Rule might be limited, exploring Lindley’s work on Bayesian statistics could provide a deeper understanding of the underlying concepts. You can search for his books or articles on Bayesian reasoning.
- Books: “The Logic of Scientific Discovery” by Karl Popper While not exclusively about Cromwell’s Rule, Popper’s philosophy of science emphasizes the importance of falsifiability and the tentativeness of scientific knowledge, which aligns well with the principles behind Cromwell’s Rule.
- Articles and Papers: “Cromwell’s Rule and the Strong Likelihood Principle” by Michael Goldstein This paper delves into the application of Cromwell’s Rule within Bayesian statistics and discusses its implications for scientific inference.
- Online Resources: This entry provides a comprehensive overview of probability theory, including discussions on Bayesian probability, which is closely related to Cromwell’s Rule.
- Videos and Lectures: Cromwell’s Rule encourages maintaining epistemic humility by avoiding absolute certainties in probabilistic reasoning.
- Belief calibration: Cromwell’s Rule concerns how strongly the available evidence warrants belief, disbelief, or suspension of judgment.
What ties this page together.
The best route is to track how evidence changes credence, how justification differs from psychological comfort, and how skepticism can discipline thought without paralyzing it.
The recurring pressure is false certainty: treating a feeling of obviousness, a social consensus, or a useful assumption as if it had already earned the status of knowledge.
Keep Cromwell’s Rule: An Elaboration, Hypothetical Discussion on Cromwell’s Rule, and Resources on Cromwell’s Rule in the same frame. That is what shows what the page is claiming, where it gets tested, and what would have to change if the claim is right.
Read this page as part of the wider Epistemology branch: the prompts point inward to the topic, but they also point outward to neighboring questions that keep the topic honest.
- Which online resource provides a comprehensive overview of probability theory, including discussions relevant to Cromwell’s Rule?
- What is the name of the principle that discourages assigning probabilities of 0 or 1 (except for logical truths)?
- According to the discussion, why should we avoid assigning absolute probabilities in most situations?
- Which distinction inside Cromwell’s Rule is easiest to miss when the topic is explained too quickly?
- What is the strongest charitable reading of this topic, and what is the strongest criticism?
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This page belongs inside the wider Epistemology branch and is best read in conversation with neighboring topics. Use the branch guide, concept tags, and reading paths to keep the question moving rather than treating the page as a polite dead end.