[ad. L. convers-us turned about, transformed, pa. pple. of convertĕre: see CONVERT. La converse occurs in F. from 13th c., = Pr. and med.L. conversa.]
A. adj.
1. Turned round; opposite or contrary in direction or action; acting in reverse manner.
1794. Sullivan, View Nat., I. 355. The transformation of vapour into air [and] the converse change.
1862. H. Spencer, First Princ., I. iv. § 26. As in this case … so in the converse case.
1873. Burton, Hist. Scot., VI. lxxi. 218. The converse arts of destruction and defence.
1876. Gladstone, Synchr. Homer., 227. Now of Zephuros Euros is the converse wind from the opposite point of heaven.
† 2. Math. Converse ratio, proportion: see quots.
1570. Billingsley, Euclid, V. Def. xiii. 134. Conuerse proportion, or proportion by conuersion is, when the consequent is taken as the antecedent, and so is compared to the antecedent as to the consequent.
1660. Barrow, Euclid, V. Def. xvi. Converse ratio is when the antecedent is compared to the excess wherein the antecedent exceeds the consequent.
1695. Alingham, Geom. Epit., 19. Converse Reason or proportion is the comparing the Antecedent to the excess, wherein the Antecedent exceeds the Consequent.
B. sb.
1. gen. A statement or form of words derived from another by the turning about or transposition of two important antithetical members; e.g., ‘the possession of wealth without learning,’ ‘the possession of learning without wealth’; ‘a quiet day and a noisy night,’ ‘a noisy day and a quiet night.’ [This use occurs in OF. in 13th c.]
1798. Malthus, Popul. (1878), 240. The converse of this will be also true.
1841–4. Emerson, Ess., Compensation, Wks. (Bohn), I. 41. The theory of the mechanic forces is another example. What we gain in power is lost in time; and the converse.
1855. Maury, Phys. Geog. Sea, ix. § 446. A series of observations the converse of this, viz. winter in the North Atlantic, summer in the South.
1861. Tulloch, Eng. Purit., ii. 278. ‘All wickedness is weakness.’ The converse he seems to have believed.
1875. Jowett, Plato (ed. 2), III. 23. The thesis … is the converse of that of Thrasymachus … not right is the interest of the stronger, but right is the necessity of the weaker.
b. A thing or action that is the exact opposite of another. [Occurs in OF. in 14th c.]
1786. Tooke, Purley (1840) 11. They travelled backwards, and sought for the things from the signs: adopting the converse of the principle; namely, that there must be as many differences of things as of signs.
1802. Paley, Nat. Theol., xxi. 330. By evaporation water is carried up into the air; by the converse of evaporation, it falls down upon the earth.
1833. M. Scott, Tom Cringle, xiii. (1859), 295. She was the very converse of our old ship, she never missed stays although I did cruelly.
a. 1852. D. Webster, Wks. (1877), III. 453. The natural converse of accession is secession; and therefore when it is stated that the people of the States acceded to the Union, it may be more plausibly argued that they may secede from it.
1869. T. Graham, in Sci. Opinion, 10 Feb., 270/2. This contraction of the wire is in length only. The result is the converse of extension by wire-drawing.
1879. Mallock, Life worth Living, 135. The positions of the two moralists are in fact the exact converses of each other.
2. Math. (One proposition is the converse of another, when the datum and conclusion of the one are respectively taken as the conclusion and datum of the other.)
1570. Billingsley, Euclid, I. vi. 16. The 8 proposition being the conuerse of the fourth.
1660. Barrow, Euclid, I. axiom viii., note. Things which agree together are equal one to the other. The converse of this Axiome is true in right lines and angles, but not in figures, unless they be like.
1726. trans. Gregory’s Astron., I. 53. The Converses of these are evident.
Mod. This proposition is the converse of the preceding.
3. Logic. A converted proposition: formerly applied to the original proposition upon which conversion is performed (called by Hamilton the CONVERTEND), but now usually to that which results from converting the original.
1827. Whately, Logic, II. ii. § 4. Conversion can then only be illative when no term is distributed in the Converse, which was not distributed in the Exposita.
1837–8. Sir W. Hamilton, Logic, I. 256. The original or given proposition is called the Converse or Converted … It would be better to call [it] the Convertend … This language I shall use. Ibid., I. 257. The Quantity of the Proposition in Conversion remains always the same; that is, the absolute quantity of the Converse must be exactly equal to that of the Convertend.
1884. Jevons, Stud. Deduct. Logic, 32. It must be observed that the converse, obverse, and contrapositive are all true if the original proposition is true.
