# Questions tagged [formal-theory]

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### Model vs Theory: Meanings reversed in Alfred Tarski vs Julian Jaynes?

In my reading of Alfred Tarski's model theory, a theory is a formal system whose sentences are without inherent meaning, but which becomes meaningful (e.g. having truth values) only after a model ...
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### Looking for help understanding modal logic and graph structure

I'm a novice to modal logic and only have a passing familiarity with classical logic. I started reading 'Modal Logic for Open Minds'. It is very readable, but then on page 16 the author introduces a ...
163 views

### Does try-catch from programming has any basis in formal logic or mathematics and if so what is it?

Does try-catch from programming has any basis in formal logic or mathematics and if so what is it?
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### Does Tarski Indefinability theorem impose a computational lower bound on the axiomatization of the reality?

Based on the Tarski's Indefinability Theorem (TA in standard model is not arithmetic (no FOL formula can represent TA, a formula represent a predicate relation definition: under Tarski's first order ...
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### Introduction to Formal Metaphysics

As I am very interested in Edward Zalta's research in Axiomatic Metaphysics, I wanted to read up on Formal Metaphysics. Would there be some introductory material that would help? Thank you in advance ...
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### Are the terms formula and algorithm synonymous in formal logic?

How to do something in two or more steps would feel/grasped to me as pretty much matching the common usages of both terms, but to find possible nuances common in the philosophical literature in ...
115 views

### What are sufficient grounds for establishing a theory?

This question delves into the definition of a theory, but somewhat into the grounds of Set Theory as well. I was wondering on what grounds is theory established and accepted. To what degree do the ...
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### How philosophers reason about closeness of one theory to the other theory (approximation, learnability, discovery of theory)?

Some theory is tuple of set of axioms (including ones that are statements about data), set of inference rules and set of already deduced theorems (statements) in it. Theory can be discovered by human ...
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### Is it there a "completely expressive" formal system / logic language?

I wonder whether it exists a formal system such that all (or a considerable number of) the others can be considered as a subsets or fragments of it. I would say that, for instance, First-Order logic ...
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### What is the 'axiomatic' or epistemological foundation of Analytic philosophy, what is its practice and purpose?

In researching the origin and purpose of the Analytical Tradition in philosophy, all that appeared was that it traces its origin to the 'Tractatus' offshoots following Wittgenstein and Russell, and ...
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### Life as a formal system

I am curious if there is some existing work on viewing life as a formal system. In formal system we have: axioms and rules of logic (like in math AND, OR) then we derive and prove theorems I see ...
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### Bibliography about non-mathematical applications of logic:

I have been recently playing with modal and temporal modal logics in the context of "organisms" (mostly after some study of entelechy in Aristotle and relatedly, some ideas of current biology). I have ...
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### Necessity of multiple theories to understand our world

I understand that in any branches of knowledge or fields, there are theories which do well in describing one or possibly more than one phenomena. However, any theory has its limitations and cannot be ...
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### Why is there no "Mario Bunge" entry in the SEP? Where could I find a valuable presentation of Mario Bunge's philosophy?

I only have a rudimentary knowledge of Mario Bunge's philosophy. But what I've read in the Ontology part of his Treatise of basic philosophy seems much promising. I'm astonished that Bunge is not ...
1 vote
130 views

### Formal proof errors

I am trying to prove A ^ B from the premises shown in the screenshot. As you can see in the screenshot I am struggling with the second sub-sub proof. Do you have recommendations for how to continue/...
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### Why is first-order logic defined as a collection of formal systems?

I think I understand what a formal system is and what formal languages are. But I have trouble grasping why first-order logic is referred to as a collection of formal systems whereas propositional ...
1 vote
279 views

### What does Tarski mean when he says that truth is a property of sentences?

A fundamental statement of Tarski's Theory of Truth is that truth is a property of sentences. What does this statement mean? What kind of Truth is it referring to? What is the formal definition of '...
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### Is the phenomenom of “subjective consciousness” or “qualia” formally captured by any state-of-the-art Theoretical Model in Physics?

Is the phenomenon of "subjective consciousness" or "qualia" formally captured or defined by any state-of-the-art Theoretical Model in Physics? If so, can you share a brief summary of such ...
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### What is the difference between logic and mathematics?

I’ve read the article in the SEP about the philosophy of mathematics. I believe I follow most of it. However, I am a bit puzzled by something that may be due to some basic misunderstanding on my part. ...
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### Formal epistemology starting point

After an introductory course in logic (propositional and predicate calculus) and the article on the SEP, where and how should one start studying formal epistemology?
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### Is it valid to prove the axioms of a system from themselves? How does it square with Gödel's incompleteness?

I recently asked whether the axioms are tautologies, and got comments that seemed to me highly suspicious. Namely, that you can always prove an axiom from itself, that you can trivially say A ...
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### What is the difference between Herbrand Logic, Relational Logic and Predicate Logic?

I am learning a course from Stanford University, and it introduces the notion of Herbrand Logic. However in Wikipedia I cannot find a definition specifically for "Herbrand Logic", only for Herbrand ...
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### Can you list examples of problems that can not be solved within a formal system but human beings have solved through construction or creativity?

This kind of problem is mentioned in a book I have read, but the book did not give a concrete example. If any such problem existed, this might help me understand human creativity. I think it would ...
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### Formal proof : predicate logic

This is what I need to prove formally: 1.∃x Cube(x) ∧ Small(d) . . . . Goal :∃x (Cube(x) ∧ Small(d)) I have already tried different ways, but I still can't prove the goal. 1. ∃x Cube(x) ∧ Small(d) ...
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### In what sense is set theory the "meta theory" of analysis?

Here, Terence Tao said: I deliberately chose not to be excessively formal with regards to the set-theoretic foundations of mathematics here, which I am regarding as part of the metatheory of ...
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### Is there (or does something exist that is close to) a theory of arguments?

I'm looking for any extensive work on a framework for "arguments", that works something along these lines: When two parties are debating, they are making assertions on a particular domain, D. Those ...
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### Derivation of the law of the conditional using the disjunct form

How can we prove that P ⊃ Q is logicaly equivalent to ¬P ∨ Q using the laws of derivation? Thank you very much in advance!
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### What are computable numbers, and what is their philosophical significance?

What are Computable Numbers? Is computability (or non-computability) some sort of technology-dependent characteristic of numbers (via e.g. Turing Machines)? What are the philosophical implications or ...
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### Is there a way to avoid Gödel's incompleteness affecting mathematics as a whole?

I have been thinking about Gödel's incompleteness theorems and their ramifications for the whole of mathematics. In this question I assume some fixed formal system F expressive enough for the ...
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### What is(are) the importance(s) of formal reasoning

In Mathematics, we as an undergraduate are exposed for the first time (at least for me it was the case) to 'rigor'. For example, in Real Analysis classes we often use logical quantifiers in our ...
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### What are the "undefinable numbers" in real analysis and philosophy?

What if any important results in real analysis make use of the notion of an "undefinable" real number? (Whatever "important" may mean to the reader.) Or is it used more in the philosophy of ...
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Some of the answers and comments to this question got me thinking about the problem of personal inadequacy. By this I mean, people seem to regularly hold values/ideals/morals beyond anything they ...
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### Where did Gödel write that first-order logic is the "true" logic?

In "On How Logic Became First-Order" Matti Eklund writes (p. 2/148): It appears to be widely held today that arguments from Skolem and Kurt Gödel, both alleged proponents of the thesis that ...
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### Was there a Kantian influence on Hilbert's formalist programme?

In this paper by Cassou-Nogues which is on an aspect of the mathematical philosophy of Cavailles he quotes the mathematician Hilbert (a colloborator of Einstein in Gottingen) ...We find ourselves ...
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### Prove a logical formula is equivalent to the contradiction if and only if the set it describes is empty

Let ψ be a well-formed-formula (wff). Prove that (ψ ≡ ⊥) ⇔ {x:ψ(x)}=Ø that is, the formula ψ is a contradiction if and only if the set it describes has no members. Note This question is not about ...
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### Are there rules for dealing with self-reference "paradoxes" in logic?

My favorite paradox that leads to an endless regress, and also leads to a question: The sentence after this is true. The sentence before this is false. When contradictions appear in proofs, we have ...
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### What is the minimum number of axioms required for a system of axioms?

What is the minimum number of axioms you need, apart from definitions and usage of the notation, such that you have a system that does not contradict itself? I would just think that the answer is ...
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### Transitive Incompleteness of Logical WFF's Due to Godel's Incompleteness Theorem

If a set of theorems, or wff's, are used in conjunction with one another, does this have an impact on their completeness in terms of soundness? For example, I have five theorems of logic, or well-...
866 views

### How does abstraction/generalization in mathematics fit into inductive reasoning?

I have a question about the nature of generalization and abstraction. Human reasoning is commonly split up into two categories: deductive and inductive reasoning. Are all instances of generalization ...
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### Definition of concept

What definition does contemporary analytic philosophy give of 'concept'? And what is the difference between a concept of something and a conception of something? Then what's the difference between ...
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### Logic as a (bad) model language

Can someone name the most well known philosophers to explicitly put forward an idea along the lines that formal systems can only be used descriptively, not prescriptively - that they're just a model, ...
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### What are the ramifications of the limitations of ZFC set theory?

In the Wikipedia article on Zermelo-Fraenkel set theory says that the theory sets out to formalize a notion of sets such that "all entities in the universe of discourse are such sets." It goes on to ...
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### How does “higher-order logic” differ from “normal” (first order?) predicate logic?

How does “higher-order logic” differ from “normal” predicate logic? I assume the latter is consistently called ”first order logic”. So where are the differences between these? What kinds of statements ...
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### Is First Order Logic (FOL) the only fundamental logic?

I'm far from being an expert in the field of mathematical logic, but I've been reading about the academic work invested in the foundations of mathematics, both in a historical and objetive sense; and ...
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### Is there a formal presentation of Maturana's "Autopoiesis"

I have been reading through "Autopoiesis and Cognition" by Humberto R. Maturana and Francisco J. Varela. One of their goals in defining autopoiesis and the supporting concepts of simple and composite ...
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### Is it possible to scientifically determine good and evil?

Sam Harris has argued on many occasions - the earliest of which I'm aware of being in his book, The End of Faith, as well as later on in The Moral Landscape - that it is (at least theoretically) ...
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