" logic, n.
Forms: 4–5 logik, 4–6 logyk(e, 4–7 logike, logique, 6 logycke, 6–7 logicke, 7–8 logick, 6– logic.
[a. F. logique (13th c.), ad. med.L. logica, ad. Gr. λογική (first found in Cicero; ellipt. for ἡ λογικὴ τέχνη, rendered in med.L. by ars logica), fem. of λογικός (whence L. logicus) pertaining to reasoning, f. λόγος word, oration, reasoning, reason, etc.: see Logos. The word is current in all the mod.Rom. and Teut. langs.: Sp. lógica, Pg., It., Du. logica, Sw. logika, Ger., Da. logik. Cicero uses also logica neut. pl. = Gr. τά λογιρά ‘logics’ (see 1 b below).]
1. a.1.a The branch of philosophy that treats of the forms of thinking in general, and more especially of inference and of scientific method. (Prof. J. Cook Wilson.) Also, since the work of Gottlob Frege (1848–1925), a formal system using symbolic techniques and mathematical methods to establish truth-values in the physical sciences, in language, and in philosophical argument. The proper scope of this department of study has been and is much controverted, and books on ‘logic’ differ widely in the range of subjects which they include. The definition formerly most commonly accepted is ‘the art of reasoning’; for various modern definitions see the later quots. At all times the vulgar notion of ‘logic’ has been largely that it is a system of rules for convincing or confounding an opponent by argument. In the Middle Ages logic (or dialectic, q.v.) was one of the three sciences composing the ‘trivium’, the former of the two divisions of the seven ‘liberal arts’.
1362 Langl. P. Pl. A. xi. 127 Lo, logyk I lered hire and al þe lawe after. c 1386 Chaucer Prol. 286 A Clerk ther was of Oxenford also, That unto logik hadde longe ygo. 1387 Trevisa Higden (Rolls) III. 251 Permenides satte ten ȝere on a roche, and byþouȝt hym of þe art of logik. 1390 Gower Conf. III. 366 Sche made him such a Silogime, That he foryat al his logique. 1481 Caxton Myrr. i. viii. 34 The seconde science is logyke.‥ This science proueth the pro and the contra. 1551 T. Wilson Logike A 1 b, Logike is an arte to reason probablie. 1593 Nashe Christ's T. 49 b, Law, Logique, and the Swizers, may be hir'd to fight for any body. 1605 Bacon Adv. Learn. ii. xviii. §5 (1891) 179 Logic differeth from rhetoric‥in this, that logic handleth reason exact and in truth, and rhetoric handleth it as it is planted in popular opinions and manners. 1707 Floyer Physic. Pulse-Watch 12 Galen brings too much Logick into his Treatise of Pulses, and mentions the Predicaments [etc.]. 1776 Adam Smith W.N. v. i. (1869) II. 354 Logic, or the science of the general principles of good and bad reasoning. 1837 Sir W. Hamilton Logic i. (1866) I. 4 Logic is the Science of the Laws of Thought as Thought. 1843 Mill Logic Introd. (1846) 9 Logic is not the science of Belief, but the science of Proof, or Evidence. 1870 Jevons Elem. Logic i. 1 Logic may be most briefly defined as the Science of Reasoning. 1903 B. Russell Princ. Math. i. i. 4 But now Mathematics is able to answer, so far at least as to reduce the whole of its propositions to certain fundamental notions of logic. 1932 Lewis & Langford Symbolic Logic v. 118 This logistic method requires that the first branch of logic to be developed should be the calculus of propositions. 1967 A. E. Blumberg in Encycl. Philos. V. 13/1 What distinguishes modern from ancient and traditional logic is not only its reliance on symbolic techniques and mathematical methods but also its vastly greater formal power and range of application. 1969 F. Mondadori in R. Klibansky Contemp. Philos. III. 352 The phenomenological foundation of logic will make a basic use of Gödel's theorem.
b.1.b pl. in the same sense. (Cf. ethics, etc.) Not now in general use.
1637 Gillespie Eng. Pop. Cerem. iii. vii. 120, I remember, that I heard in the logicks, of pars essentialis or Physica. 1651 J. Jane Εικων Ακλαστος 247 The Libellers Logickes serves him to as litle purpose, as his historie. 1698 J. Keill Exam. Theory Earth (1734) 89 The Theorist in this part has endeavoured to give us a proof of his great skill in Logicks. 1862 Dublin Univ. Cal. 48 The following books have been appointed for the Examination for Logical and Ethical Moderatorships:—Logics. All the Logics of the Undergraduate Course.
¶c.1.c Used by translators and expounders of Hegel for: The fundamental science of thought and its categories (including metaphysics or ontology).
1838 Penny Cycl. XII. 99/2 Hegel divides philosophy into three parts:—1. Logic, or the science of the idea in and by itself. 1854 A. Tulk tr. Chalybäus' Speculat. Philos. 313 Philosophy‥has three cardinal divisions,—the Logic, which with Hegel, as is readily seen, implies also Metaphysics; the Philosophy of Nature; and Philosophy of Mind. 1874 W. Wallace Logic of Hegel i. §9 Speculative Logic contains all previous Logic and Metaphysics. 1890 W. S. Hough tr. Erdmann's Hist. Phil. II. 686 The fundamental science, which Hegel calls Logic, but remarks at the same time that it may equally well be called Metaphysics or Ontology.
2. a.2.a A system or a particular exposition of logic; a treatise on logic. Also, the science or art of reasoning as applied to some particular department of knowledge or investigation.
1377 Langl. P. Pl. B. xii. 267 To lowe lybbyng men þe larke is resembled; Arestotle þe grete clerke suche tales he telleth; Thus he lykneth in his logyk þe leste foule oute. 1594 R. Ashley tr. Loys le Roy 125 b, They which write for the most part, do nothing but‥heape one on another Grammars, Rhetoricks, Logicks, Institutions [etc.]. 1699 Bentley Phal. xi. 296 If Mr. B. had studied his new Logic more and his Phalaris less; he had made better work in the way of Reasoning. 1756 Burke Subl. & B. Introd., Wks. I. 96 The logick of taste, if I may be allowed the expression. 1833 Sir W. Hamilton Discuss. (1853) 165 The arbitrary laws of our present logics. 1838 ― Logic App. (1866) II. 244 The Italian and Latin Logics of Genovesi are worthy of your attention. 1880 W. Wallace in Encycl. Brit. XI. 619/2 The logic of Hegel is the only rival to the logic of Aristotle.‥ His logic is an enumeration of the forms or categories by which our experience exists. 1882 R. Adamson ibid. XIV. 782/1 The metaphysical logic of Hegel, the empirical logic of Mill, the formal logic of Kant. 1884 Mind Jan. 123 In that speculative domain [Germany], Logics swarm as bees in spring-time.
b.2.b In phr. the logic of ―, indicating the application of logical methods to other subjects of investigation or study; the inferential procedures or structure of some field of inquiry.
1845 Mill in Westm. Rev. XLIII. 319 By the logic of a science we understand its method; its particular modes of investigation, and the nature of its evidence. 1882 A. Bain John Stuart Mill iii. 87, I was at the meeting, and listened to Herschel's address. One notable feature in it was the allusion to the recent works on the Logic of Science, by Whewell and Mill especially. 1934 Mind XLIII. 101 Little puzzles about the logic of classes. 1937 A. Smeaton tr. Carnap's Logical Syntax of Lang. iv. §70. 256 All the foregoing systems of the logic of modalities‥have, it seems, applied the quasi-syntactical method. 1942 R. G. Collingwood New Leviathan xxxi. 252 As mathematics is the logic of physics, so law is the logic of politics. 1945 Mind LIV. 175, I now regard semantics as the fulfilment of the old search for a logic of meaning, which had not been fulfilled before in any precise and satisfactory way. 1971 Kopnin & Narsky in R. Klibansky Contemp. Philos. IV. 321 The elaboration of these problems has led to the necessity of investigating the logic of contemporary scientific knowledge.
3. a.3.a Logical argumentation; a mode of argumentation viewed as good or bad according to its conformity or want of conformity to logical principles. to chop logic: see chop v.2 8. Also, logical pertinence or propriety.
1601 Bp. W. Barlow Serm. Paules Crosse Pref. 7 Malice marres logike and charitie both. 1646 Sir T. Browne Pseud. Ep. i. iv. 15 This was the Logick of the Jews, when they accused our Saviour unto Pilate. 1647 Clarendon Hist. Reb. i. §150 But when they‥instead of giving were required to pay, and by a logic that left no man any thing which he might call his own. 1738 Johnson London 71, [I] A statesman's logick unconvinced can hear. 1795 Gentl. Mag. 541/1 You will be astonished at the logick which could draw such an inference from that address. 1830 Macaulay Rob. Montgomery Ess. (1887) 140 We should be sorry to stake our faith in a higher Power on Mr. Robert Montgomery's logic. 1843 Carlyle Past & Pr. iii. v, Driven alike by its Logic, and its Unlogic. 1850 Mrs. Browning Poems I. 4 Gab. Depart. Luc. And where's the logic of ‘depart’? 1863 E. V. Neale Anal. Th. & Nat. 33 As‥Sir William Hamilton argues with overpowering learning and logic. 1891 Daily News 23 Mar. 4/7 England, as Mr. Disraeli once said, is not governed by logic.
b.3.b transf. A means of convincing or proving. Phr. the logic of the situation, the facts which dictate what action is rationally to be taken.
1682 G. Topham Rome's Tradit. Ep. Ded., Bonner's Logick, Fire and Faggot. 1711 Addison Spect. No. 239 ⁋8 A certain Grand Monarch‥writ upon his Great Guns—Ratio ultima Regum, The Logick of Kings. 1816 Sporting Mag. XLVIII. 180 On setting to Lancaster cleanly hit Ford down; when it was loudly vociferated ‘What do you think of that for logic’? 1859 E. FitzGerald tr. Omar xliii. (1899) 83 The Grape that can with Logic absolute The Two-and-Seventy jarring Sects confute. 1869 J. Eadie Comm. Gal. 133 The logic of their facts was irresistible. 1876 W. James Coll. Ess. & Rev. (1920) 34 The very essential logic of the situation demands that we wait not for any outward sign. 1880 Daily Tel. 28 Oct., The ‘logic of events’ may prove too strong for them, and what reason could not effect necessity may enforce. 1901 Scotsman 14 Mar. 7/5 Their territory‥was annexed to the British domain in consequence of the terrible logic of war. 1945 K. R. Popper Open Soc. II. xiv. 90 The detailed determination of his action by what we may call the logic of the situation. 1946 E. Wilson Mem. Hecate County (1951) iv. 117 The logic of the situation impelled me to force her backwards, dropping one hand to her waist. 1960 Rep. Proc. Conf. Univ. U.K. 58 For the ambitious young man, the logic of the situation (which fortunately doesn't wholly govern his conduct) is this: time given to teaching is time taken from research; and his future depends not on teaching, but on research. 1961 Observer 19 Nov. 11/8 He said that Mr. Gaitskell had taken up the position of outside-right, and that the logic of the situation was for him to reorganise his team so that it would at least be facing in the same direction. 1969 H. Perkin Key Profession v. 214 The logic of the situation was that the C.A.T.s should seek to complete their upgrading by seeking recognition as universities.
4.4 Computers and Electronics. a.4.a The system or principles underlying the representation of logical operations and two-valued variables by electrical or other physical signals and their interactions; the forms and interconnections of logic elements in any particular piece of equipment, in so far as they relate to the interaction of signals and not to the physical nature of the components used; also, the actual components and circuitry; logical operations collectively, as performed by electronic or other devices.
1950 W. W. Stifler High-Speed Computing Devices v. 62 For the convenient operation of a general-purpose machine, they [sc. Burks, Goldstine, and von Neumann] point out, it is essential that some steps be taken to translate the nonconforming command quoted above to the same stereotype form. This translation of description of all possible operations to prescribed forms has been called the logic of the machine by these authors, and the term is now in general use. 1952 Math. Tables & Other Aids to Computation VI. 42 It is possible, with this new approach, to obtain many of the advantages of a digital computer and also the essential advantages of an analog differential analyzer. The result is a different type of digital ‘logic’ from that used in the general purpose digital computer. 1954 IRE Trans. Electronic Computers Mar. 33/2 The authors have presented the more general aspects of the machine in block diagram form and in addition have given pertinent illustrations of the instrumentation of the logic. 1956 Ibid. IV. 134 (caption) Logic for self-timing full length carry. 1962 Simpson & Richards Physical Princ. Junction Transistors xvi. 401 If we now define the most positive value of the output to represent a ‘one’ and the most negative value a ‘zero’ in a binary system of arithmetic (the positive logic system) the emitter followers form an ‘and’ gate, i.e. all n inputs must be ‘one’ if the output is to be ‘one’. 1967 Electronics 6 Mar. 26 Santa Clara was making milliwatt resistor–transistor logic for the project. 1968 Proc. Inst. Electr. Engin. CXV. 1385/2 He separated the ternary circuits into two sets of binary circuits, one based on a positive logic and the other on a negative one. Then he used translating circuits between the two logics and achieved a true ternary output with the aid of a combining circuit. 1970 New Yorker 11 Apr. 34 The computer logic is so fast that it has to loaf at several intervals while the input and output devices‥are printing information. 1971 New Scientist 25 Mar. 692 The technology [of fluidics] was developed basically to provide a system of control logic and power amplification in the adverse environment of space. 1973 Nature 20 Apr. 494/2 The transistor has endowed tremendous scope for performing electronic functions (for example switching, which permits binary logic, and amplifying, which makes possible many other forms of signal processing).
b.4.b attrib., as logic design, logic designer, logic diagram, logic function, logic module, logic network, logic operation, logic state; logic circuit, a circuit for performing logical operations and consisting of one or more logic elements; logic element, a device (usu. electronic) for performing a logical operation, in which the past or present values of one or more inputs determine the values of one or more outputs in accordance with a simple scheme which most commonly involves, in effect, only two possible values for the signals; logic gate, a logic circuit that is a gate (gate n.1 8 g).
1953 Communications & Electronics (N.Y.) Nov. 593/1 The search for simple abstract techniques to be applied to the design of switching systems is still‥in its early stages. The problem in this area which has been attacked most energetically is that of the synthesis of efficient combinational that is, nonsequential, logic circuits. 1959 K. Henney Radio Engin. Handbk. (ed. 5) ix. 7 Very complicated logic circuits involving many thousands of diodes have been assembled for use in electronic computers. 1968 Times 18 Oct. 16/5 Computer logic circuits based on the ternary system of arithmetic have been devised by two engineers.‥ They have devised logic circuits that perform the basic arithmetical operations in ternary numbers.
1956 IRE Trans. Electronic Computers V. 132/2 The evolution of a set of standard logical circuit blocks allows this design without direct reference to the circuits, thus reducing logic design to the application of a set of rules expressing the input and output capabilities of each of the logical circuit blocks. 1972 D. Zissos Logic Design Algorithms p. v, Complex switching circuits are used extensively, not only in the logic design of systems such as digital computers and message-switching networks, where they are the subject of study by specialist logic designers, but also for purposes of industrial control and automation.
1956 Logic designer [see logical a. 1 b].
1962 Gloss. Terms Automatic Data Processing (B.S.I.) 59 Logic diagram, a graphical representation of the logic design. 1971 J. H. Smith Digital Logic iv. 54 There are a number of different circuits which will carry out this function and it is normal to use the symbol of the circuit employed when drawing logic diagrams.
1959 C. V. L. Smith Electronic Digital Computers iv. 106 This technique makes it possible to make large arrays of logic elements in very compact form. Ibid. (heading) Symbols for logic elements. 1969 P. B. Jordain Condensed Computer Encycl. 291 A sequential logic element has an output determined by present and past input signals: it has some degree of retention, or memory. 1971 New Scientist 25 Mar. 692 The technology of fluidics is divided into‥pure fluidic techniques which use a logic element with no moving parts, and the method using moving part logic.
1959 K. Henney Radio Engin. Handbk. (ed. 5) ix. 7 Since diodes have two distinctly differing impedance levels, they lend themselves to use in performing predetermined decision or logic functions just as switches or relays may.
1961 Times 3 Oct. (Computer Suppl.) p. v, What the technical terms (binary, logic gates, programme and many others) mean. 1967 Electronics 6 Mar. 45/3 Each cell will have a working structure, or ‘base’, of 13 logic gates, plus 13 flip-flops.
1971 J. H. Smith Digital Logic iv. 40 It is usually unnecessary to design logical circuitry today, as many manufacturers supply logic modules to carry out the more common forms of logic. 1974 Physics Bull. Mar. 113/1 Ortec will be displaying the new fast logic modules in the M300 series.
1961 Engineering 17 Feb. 269/1 The first step in designing the computer was the synthesis of the logic network to perform the necessary functions.
1970 Nature 12 Sept. 1092/2 The most exciting possibility for these devices lies naturally in their use as shift registers and for logic operations in computers.
1973 Sci. Amer. Nov. 14/1 (Advt.), In a digital circuit, the important thing is to know the logic state of a node, whether it's above the threshold voltage and therefore a logic high, or below the threshold voltage and therefore a logic low.
5.5 attrib. = of or pertaining to logic. In some of the earlier quots. possibly a real adj. (like L. logicus, F. logique) = logical 1.
1581 J. Hamilton Catholik & Facile Traictise 19 Zung men neu cum out of the grammer or logic scholes. 1608 T. Morton Preamble Encounter 107, I haue now my Mitigator vpon a Logicke racke. 1613 Jackson Creed ii. ii. §6 Most of them vsually penned in a base and barbarous Logicke phrase. 1628 T. Spencer Logick 36 This distinction, is received in all the Logick schooles. 1635 E. Pagitt Christianogr. ii. vii. (1636) 79 Endeavoring to enthrall us with sophisticall arguments and Logick quirks. 1652 J. Collinges Caveat for Prof. (1653) A iij b, They would not endure to stand in a Logick forme. 1678 Gale Crt. Gentiles III. 8 Sin is not a mere nothing, but has some kind of logic positivitie or notional entitie. 1724 R. Wodrow Life J. Wodrow (1828) 18, I had a copy of Logick and Ethick Dictates in my father's hand among his school books. 1742 Young Nt. Th. ix. 865 Wouldst thou on metaphysic pinions soar? Or wound thy patience amid logic thorns? 1843 Carlyle Past & Pr. iii. v. 223 Questions insoluble, or hitherto unsolved; deeper than any of our Logic-plummets hitherto will sound. 1869 Browning Ring & Bk. viii. 243 He'll keep clear of my cast, my logic-throw.
6.6 Comb.: logic-book; (sense 3) logic-chopper, logic-chopping; †logic-fisted a., having the hand clenched, like Logic in personification (see Cic. Orat. xxxii. 113; Bacon Adv. Learn. ii. xviii. §5); logic-tight a. [after watertight a. 1], impervious to logic or reason.
1685 tr. Arnauld & Nicole's Logic 17 We should give a reason for omitting so many questions as are found in the common Logic-Books. 1895 W. James Coll. Ess. & Rev. (1920) 394 An hypothesis, we are told in the logic-books, ought to propose a being that has some other constitution and definition than that of barely performing the phenomenon it is evoked to explain. 1906 Daily Chron. 13 Mar. 6/2 Mr. Balfour‥made his reappearance in his old part of the Logic-chopper. 1924 R. Graves Mock Beggar Hall 32 Put it another way, thou logic-chopper. 1956 J. Blish Earthman, Come Home i. 33 You have no ties, no faith. You will have to excuse ours. We cannot afford to be logic-choppers.
1904 W. James in Mind XIII. 458 This is a kind of intellectual product that never attains a classic form of expression when first promulgated. The critic ought therefore not to be too sharp and logic-chopping in his dealings with it. 1960 Koestler Lotus & Robot i. iii. 132 The Schoolmen confined themselves to verbal logic-chopping.
1683 Kennett tr. Erasm. on Folly 80 One, with an open-handed freedome, spends all he lays his fingers on; another with a Logick-fisted gripingness, catches at, and grasps all he can come within the reach of.
1912 B. Hart Psychol. Insanity vi. 82 The delusion is preserved in a logic-tight compartment. 1968 P. McKellar Experience & Behaviour x. 269 The widespread tendency‥to surround their favourite beliefs with logic-tight compartments.
Add: [4.] [b.]4.b logic bomb, a series of instructions surreptitiously incorporated in a program in such a way that if a particular logical condition is ever satisfied, the instructions will be carried out, usually with deleterious results; cf. time bomb (b) s.v. *time n. 60 a.
1978 Times 17 Nov. 23/7 Computer crime‥. The planting of instructions to come into action at a given time is known as a time bomb or logic bomb. 1986 Computer Weekly 8 May 50/3 ‘Logic bombs’ have forced at least six companies out of business in the last two years. 1987 Sunday Tel. (Colour Suppl.) 23 Aug. 40/4 His logic bomb simply ordered the program to stop if it handled his personal number in connection with his dismissal.