3,455 research outputs found
A Galois connection between classical and intuitionistic logics. I: Syntax
In a 1985 commentary to his collected works, Kolmogorov remarked that his
1932 paper "was written in hope that with time, the logic of solution of
problems [i.e., intuitionistic logic] will become a permanent part of a
[standard] course of logic. A unified logical apparatus was intended to be
created, which would deal with objects of two types - propositions and
problems." We construct such a formal system QHC, which is a conservative
extension of both the intuitionistic predicate calculus QH and the classical
predicate calculus QC.
The only new connectives ? and ! of QHC induce a Galois connection (i.e., a
pair of adjoint functors) between the Lindenbaum posets (i.e. the underlying
posets of the Lindenbaum algebras) of QH and QC. Kolmogorov's double negation
translation of propositions into problems extends to a retraction of QHC onto
QH; whereas Goedel's provability translation of problems into modal
propositions extends to a retraction of QHC onto its QC+(?!) fragment,
identified with the modal logic QS4. The QH+(!?) fragment is an intuitionistic
modal logic, whose modality !? is a strict lax modality in the sense of Aczel -
and thus resembles the squash/bracket operation in intuitionistic type
theories.
The axioms of QHC attempt to give a fuller formalization (with respect to the
axioms of intuitionistic logic) to the two best known contentual
interpretations of intiuitionistic logic: Kolmogorov's problem interpretation
(incorporating standard refinements by Heyting and Kreisel) and the proof
interpretation by Orlov and Heyting (as clarified by G\"odel). While these two
interpretations are often conflated, from the viewpoint of the axioms of QHC
neither of them reduces to the other one, although they do overlap.Comment: 47 pages. The paper is rewritten in terms of a formal meta-logic (a
simplified version of Isabelle's meta-logic
Three Essays in Intuitionistic Epistemology
We present three papers studying knowledge and its logic from an intuitionistic viewpoint.
An Arithmetic Interpretation of Intuitionistic Verification
Intuitionistic epistemic logic introduces an epistemic operator to intuitionistic logic which reflects the intended BHK semantics of intuitionism. The fundamental assumption concerning intuitionistic knowledge and belief is that it is the product of verification. The BHK interpretation of intuitionistic logic has a precise formulation in the Logic of Proofs and its arithmetical semantics. We show here that this interpretation can be extended to the notion of verification upon which intuitionistic knowledge is based. This provides the systems of intuitionistic epistemic logic extended by an epistemic operator based on verification with an arithmetical semantics too. This confirms the conception of verification incorporated in these systems reflects the BHK interpretation.
Intuitionistic Verification and Modal Logics of Verification
The systems of intuitionistic epistemic logic, IEL, can be regarded as logics of intuitionistic verification. The intuitionistic language, however, has expressive limitations. The classical modal language is more expressive, enabling us to formulate various classical principles which make explicit the relationship between intuitionistic verification and intuitionistic truth, implicit in the intuitionistic epistemic language. Within the framework of the arithmetic semantics for IEL we argue that attempting to base a general verificationism on the properties of intuitionistic verification, as characterised by IEL, yields a view of verification stronger than is warranted by its BHK reading.
Intuitionistic Knowledge and Fallibilism
Fallibilism is the view that knowledge need not guarantee the truth of the proposition known. In the context of a classical conception of truth fallibilism is incompatible with the truth condition on knowledge, i.e. that false propositions cannot be known. We argue that an intuitionistic approach to knowledge yields a view of knowledge which is both fallibilistic and preserves the truth condition. We consider some problems for the classical approach to fallibilism and argue that an intuitionistic approach also resolves them in a manner consonant with the motivation for fallibilism
Five Observations Concerning the Intended Meaning of the Intuitionistic Logical Constants
This paper contains five observations concerning the intended meaning of the intuitionistic logical constants: (1) if the explanations of this meaning are to be based on a non-decidable concept, that concept should not be that of 'proof'; (2) Kreisel's explanations using extra clauses can be significantly simplified; (3) the impredicativity of the definition of → can be easily and safely ameliorated; (4) the definition of → in terms of 'proofs from premises' results in a loss of the inductive character of the definitions of ∨ and ∃; and (5) the same occurs with the definition of ∀ in terms of 'proofs with free variables
On an Intuitionistic Logic for Pragmatics
We reconsider the pragmatic interpretation of intuitionistic logic [21]
regarded as a logic of assertions and their justications and its relations with classical
logic. We recall an extension of this approach to a logic dealing with assertions
and obligations, related by a notion of causal implication [14, 45]. We focus on
the extension to co-intuitionistic logic, seen as a logic of hypotheses [8, 9, 13] and on
polarized bi-intuitionistic logic as a logic of assertions and conjectures: looking at the
S4 modal translation, we give a denition of a system AHL of bi-intuitionistic logic
that correctly represents the duality between intuitionistic and co-intuitionistic logic,
correcting a mistake in previous work [7, 10]. A computational interpretation of cointuitionism
as a distributed calculus of coroutines is then used to give an operational
interpretation of subtraction.Work on linear co-intuitionism is then recalled, a linear
calculus of co-intuitionistic coroutines is dened and a probabilistic interpretation
of linear co-intuitionism is given as in [9]. Also we remark that by extending the
language of intuitionistic logic we can express the notion of expectation, an assertion
that in all situations the truth of p is possible and that in a logic of expectations
the law of double negation holds. Similarly, extending co-intuitionistic logic, we can
express the notion of conjecture that p, dened as a hypothesis that in some situation
the truth of p is epistemically necessary
Some Logical Notations for Pragmatic Assertions
The pragmatic notion of assertion has an important inferential role in logic. There are also many notational forms to express assertions in logical systems. This paper reviews, compares and analyses languages with signs for assertions, including explicit signs such as Frege’s and Dalla Pozza’s logical systems and implicit signs with no specific sign for assertion, such as Peirce’s algebraic and graphical logics and the recent modification of the latter termed Assertive Graphs. We identify and discuss the main ‘points’ of these notations on the logical representation of assertions, and evaluate their systems from the perspective of the philosophy of logical notations. Pragmatic assertions turn out to be useful in providing intended interpretations of a variety of logical systems
A Pragmatic Interpretation of Quantum Logic
Scholars have wondered for a long time whether the language of quantum
mechanics introduces a quantum notion of truth which is formalized by quantum
logic (QL) and is incompatible with the classical (Tarskian) notion. We show
that QL can be interpreted as a pragmatic language of assertive formulas which
formalize statements about physical systems that are empirically justified or
unjustified in the framework of quantum mechanics. According to this
interpretation, QL formalizes properties of the metalinguistic notion of
empirical justification within quantum mechanics rather than properties of a
quantum notion of truth. This conclusion agrees with a general integrationist
perspective that interprets nonstandard logics as theories of metalinguistic
notions different from truth, thus avoiding incompatibility with classical
notions and preserving the globality of logic. By the way, some elucidations of
the standard notion of quantum truth are also obtained.
Key words: pragmatics, quantum logic, quantum mechanics, justifiability,
global pluralism.Comment: Third version: 20 pages. Sects. 1, 2, and 4 rewritten and improved.
Explanations adde
A Galois connection between classical and intuitionistic logics. II: Semantics
Three classes of models of QHC, the joint logic of problems and propositions,
are constructed, including a class of subset/sheaf-valued models that is
related to solutions of some actual problems (such as solutions of algebraic
equations) and combines the familiar Leibniz-Euler-Venn semantics of classical
logic with a BHK-type semantics of intuitionistic logic.
To test the models, we consider a number of principles and rules, which
empirically appear to cover all "sufficiently simple" natural conjectures about
the behaviour of the operators ! and ?, and include two hypotheses put forward
by Hilbert and Kolmogorov, as formalized in the language of QHC. Each of these
turns out to be either derivable in QHC or equivalent to one of only 13
principles and 1 rule, of which 10 principles and 1 rule are conservative over
classical and intuitionistic logics. The three classes of models together
suffice to confirm the independence of these 10 principles and 1 rule, and to
determine the full lattice of implications between them, apart from one
potential implication.Comment: 35 pages. v4: Section 4.6 "Summary" is added at the end of the paper.
v3: Major revision of a half of v2. The results are improved and rewritten in
terms of the meta-logic. The other half of v2 (Euclid's Elements as a theory
over QHC) is expected to make part III after a revisio
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