The Complexity of Theorem-Proving Procedures
Proceedings of the third annual ACM symposium on Theory of computing - STOC '71, 1971 · paper · Computer science
Shows that any problem solved by a polynomial-time nondeterministic Turing machine can be reduced to deciding whether a propositional formula is a tautology. It also shows that problem has the same polynomial difficulty as the subgraph isomorphism problem.
Checked: PDF from cs.cmu.edu, fetched 4 Oct 2026. Page numbers are those of that PDF.
1 finding
Substance The proof of Theorem 4 prints "φ(A(w)) ≤ K (4^n)^2 = K 8^n", but (4^n)^2 = 16^n. The bound T_Q(K 8^n) in the theorem statement and in the last line of the proof rests on this equality.
- p. 6 Proof of Theorem 4
φ(A(w)) ≤ K (4n)2 = K 8n
- p. 6 Theorem 4 statement
recognized by a deterministic machine within time TQ(K 8n)
- p. 6 Proof of Theorem 4, last sentence
If no result appears within TQ(K 8n) steps
- p. 6 Proof of Theorem 4
halts within 4n steps for all computations
Only the authors can say what is right here.
Judge's note: Page 6 image clearly shows the superscripts: 'halts within 4^n steps' and 'K (4^n)^2 = K 8^n'. (4^n)^2 = 4^{2n} = 16^n, and 16^n/8^n = 2^n is unbounded, so K cannot absorb the difference. The printed equality is false, and the argument as written gives T_Q(K 16^n). M2 simulates M1 for exactly 2^n steps, so the authors may have meant a tighter step bound. Only they can say which constant is intended. The qualitative use in Section 4 survives with 16^n.
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16 minor (typos and the like; most checked by the judge only)
Wording Section 1 sets up the propositional calculus but says "Thus a formula of length n can only have about n/logn distinct function and predicate symbols"; the symbols just described are proposition symbols (atoms).
- p. 1 Section 1, first paragraph
distinct function and predicate symbols
- p. 1 Section 1, first paragraph
only have about n/logn distinct function and predicate symbols
Judge's note: Page 1 image: the sentence before this one describes proposition symbols (atoms) written as a member of Σ followed by a binary number. The 'Thus' conclusion then names function and predicate symbols, which belong to the predicate calculus of Section 3. The bound is right; the wording names the wrong kind of symbol.
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Wording The proof of Theorem 2 says "By the corollary to theorem 1, each of the sets is P-reducible to {DNF tautologies}", but the Corollary covers only "the sets in definitions 1)–5)", and {tautologies} is not one of them.
- p. 4 Proof of Theorem 2, first sentence
By the corollary to theorem 1, each of the sets is P-reducible to {DNF tautologies}.
- p. 2 Corollary
Each of the sets in definitions 1)–5) is P-reducible to {DNF tautologies}.
Judge's note: Pages 2 and 4: definitions 1)–5) are subgraph pairs, isomorphic graphpairs, Primes, DNF tautologies and D3. {tautologies} is listed in Theorem 2 but is not in that list. The reduction does follow directly from Theorem 1, by the same complement argument the Corollary uses, so the pointer is imprecise rather than mathematically wrong.
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Wording The states are declared as "{q1,...,qr}" and Q^i_t is defined for "1 ≤ i ≤ r", but formula E uses Q^0_1 with "q0 is the initial state". Neither q0 nor Q^0_t is defined.
- p. 3 Formula E, proof of Theorem 1
q0 is the initial state
- p. 3 Proposition symbols and formula E
Qi t for 1 ≤ i ≤ r, 1 ≤ t ≤ T
- p. 3 state set
the set of states is {q1,...,qr}
Only the authors can say what is right here.
Judge's note: Page 3 image confirms the state set {q1,...,qr} (footnote 4 discusses only q_s versus q_r), the range 1 ≤ i ≤ r, and E = Q^0_1 ∧ ... with 'q0 is the initial state'. The index 0 falls outside the declared range, so D does not constrain Q^0_1 as written. Either the state set or the initial-state symbol needs adjusting. The proof idea is unaffected.
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Wording In the proof of Theorem 1 (nondeterministic M), G^t_{i,j} = ⋀_s (¬Q^i_t ∨ ¬S_{s,t} ∨ ¬P^j_{s,t} ∨ Q^k_{t+1}) uses a single "q_k ... the state given by the transition function for M". For a nondeterministic M this successor need not be unique.
- p. 3 Proof of Theorem 1, definition of G^t_{i,j}
where qk is the state given by the transition function for M
- p. 3 Displayed formula for G^t_{i,j}
¬Qi t ∨¬Ss,t ∨¬P j s,t ∨Qk t+1
Only the authors can say what is right here.
Judge's note: Page 3 image confirms the clause and its wording. My own check: suppose M's transition relation allows two moves from (q_i, σ_j) with different next states q_a and q_b. Any one q_k fixed in G, together with D (exactly one state per time), forces Q^k_{t+1} and so rules out the other branch. A(w) could then be unsatisfiable even though some branch accepts, so the 'iff' would fail. The text introduces G with 'For example', and footnote 5 notes an undeciphered handwritten annotation right here. The standard repair (a disjunction over the allowed moves, tied to F and H) keeps Theorem 1. The step is faulty; the stated result stands.
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Typo The Section 1 heading reads "Tautologies and Polynomial Re-Reducibility." The body only defines "P-reducible" and "P-reducibility".
- p. 1 Heading of Section 1
Tautologies and Polynomial Re-Reducibility.
- p. 1 Section 1 heading
Polynomial Re-Reducibility
Judge's note: Page 1 image confirms the heading. The term 're-reducibility' is never defined or used anywhere else. It looks like a duplicated syllable, possibly carried over from the typescript.
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Typo The transliterator's footnote * reads "I transcripted basically exactly as Cook wrote the text"; the standard word is "transcribed".
- p. 1 Footnote *
I transcripted basically exactly
- p. 1 Footnote *
I transcripted basically exactly as Cook wrote
Judge's note: Page 1 image: footnote * shows 'transcripted'. This is a non-standard word form in the transliterator's own note.
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Typo The set is defined as "{Primes}" (Definition 3, p. 2) but written "{primes}" (italic, lower case) in the Remark after Theorem 2 (p. 3).
- p. 2 Definition 3
The set {Primes} is the set of all binary notations
- p. 3 Remark after Theorem 2
add either {primes} or {isomorphic graphpairs}
- p. 3 Remark after Theorem 2
We have not been able to add either {primes}
- p. 3 Remark
add either {primes} or
Judge's note: The images on pages 2 and 3 confirm the different capitalisation and typeface for the same set. This is cosmetic only.
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Typo In the proof of Theorem 1 the range for C_{s,t} is printed "For 1 ≤ s ≤ T and q ≤ t ≤ T_j C_{s,t} asserts..."; it should evidently read "1 ≤ t ≤ T,".
- p. 3 Definition of C_{s,t}, proof of Theorem 1
q ≤ t ≤ Tj
- p. 3 Definition of C in proof of Theorem 1
For 1 ≤ s ≤ T and q ≤ t ≤ Tj Cs,t
- p. 3 definition of C
For 1 ≤s ≤T and q ≤t ≤Tj Cs,t asserts
- p. 3 definition of C
q ≤t ≤Tj Cs,t
Judge's note: Page 3 image shows 'q ≤ t ≤ T_j'. No T_j is defined, and q denotes states elsewhere. Every other time range in the construction is 1 ≤ t ≤ T. This is a typing slip.
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Typo The paragraph after the Remark on p. 3 opens "Incidently, it is"; the correct spelling is "Incidentally".
- p. 3 Paragraph after Remark
Incidently, it is
- p. 3 after Remark
Incidently
- p. 4 Discussion
intractible
- p. 4 Discussion
preceeding
Judge's note: Page 3 image confirms 'Incidently'. Footnote 6 corrects only the missing 'is'. The other two misspellings this cluster lists ('intractible', 'preceeding') are judged separately under C009 and C010.
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Typo In the Section 2 Discussion: "many other apparently intractible problems"; this should be "intractable".
- p. 4 Section 2 Discussion, first paragraph
apparently intractible
Judge's note: Page 4 image confirms the spelling 'intractible'.
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Typo In the Section 2 Discussion: "the notions in the preceeding sections"; this should be "preceding".
- p. 4 Section 2 Discussion, last paragraph
the preceeding sections
Judge's note: Page 4 image confirms the spelling 'preceeding'.
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Typo In the proof of Theorem 2, G1 has vertices {v1,...,vk}, but the condition is written "for each i, φ(i) = u_ij for some j", applying φ to an index rather than to v_i.
- p. 4 Proof of Theorem 2, D3 to subgraph reduction
for each i, φ(i) = ui j for some j
- p. 4 Proof of Theorem 2, D3 to subgraph reduction
such that for each i, φ(i) = ui j for some j
Judge's note: Page 4 image confirms 'φ(i) = u_ij' in two places. Identifying v_i with i is a common shorthand and the meaning is clear, but the paper never states it.
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Typo The Discussion says "even if the formula is in normal disjunctive form", while the rest of the paper uses "disjunctive normal form".
- p. 4 Discussion
normal disjunctive form
Judge's note: Page 4 image confirms the phrase. Elsewhere (pp. 2 and 4) the paper says 'disjunctive normal form'. This is a minor terminology inconsistency and the meaning is clear.
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Typo Proof of 3B writes "since we can assume |A| ≤ log k" while the definition of type Q (p. 5) states the condition as "|A| ≤ log_2 k" (subscript 2).
- p. 6 proof of 3B
since we can assume |A| ≤logk
Judge's note: Page images p5 and p6 checked. The definition on p5 has log with subscript 2. The proof of 3B on p6 has plain 'log k', and 3A also uses plain log ('m ≤ log s^2'). This is a notational inconsistency only. Plain log most likely means base 2 here, and a change of base is a constant factor that cannot affect the O(k log^2 k) bound, so the argument is unaffected. Cosmetic.
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Typo Reference [7] gives the title as "Dominoes and the AEA case of the decision problems." (plural).
- p. 7 Reference [7]
Dominoes and the AEA case of the decision problems.
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that Wang's 1962 paper is titled 'Dominoes and the AEA case of the decision problem' (singular). The p7 image confirms the plural 'problems' is printed. Nothing in the files can confirm the true title, so this is an author query. At most it is a one-letter slip in the title, and the citation can still be identified.
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Typo Reference [5] reads "J. Assoc. Computing Machinery, 1960, pp. 201–215." with no volume or issue, unlike [4] ("Vol. 17, No. 1, Jan. 1970").
- p. 7 References [5]
J. Assoc. Computing Machinery, 1960, pp. 201–215.
Judge's note: The p7 reference list image confirms that [5] has only the year and pages, while [4], in the same journal, gives volume and number. This is a stylistic inconsistency in the bibliography, and the entry can still be identified from authors, year and pages. Supplying the volume and issue would rely on outside knowledge.
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