CONVERSION (Lat. conversio, from convertere, to turn or change), a general term for the operation of converting, changing, or transposing; used technically in special senses in logic, theology and law.
1. In logic, conversion is one of three chief methods of immediate inference by which a conclusion is obtained directly from a single premise without the intervention of another premise or middle term. A proposition is said to be "converted" when the subject and the predicate change places; the original proposition is the "convertend," the new one the "converse." The chief rule governing conversion is that no term which was not distributed  in the convertend may be distributed in the converse; nor may the quality of the proposition (affirmative or negative) be changed. It follows that of the four possible forms of propositions A, E, I and O (see article A), E and I can be converted simply. If no A is B (E), it follows that no B is A; if some A is B, it follows that some B is A. This form of conversion is called Simple Conversion; E propositions convert into E, and I into I. On the other hand, A cannot be converted simply. If all men are mortal, the most that can follow by conversion is that some mortals are men. This is called Conversion by Limitation or Per Accidens. Only if it be known from external or non-logical sources that the predicate also is distributed can there be simple conversion of a universal affirmative. Neither of these forms of conversion can be applied to the particular negative proposition O, which has to be dealt with under a secondary system of conversion, as follows. The terminology by which these secondary processes are described is not altogether satisfactory, and logicians are not agreed as to the application of the terms. The following system is perhaps the most commonly used. We have seen that the converse of "all A is B" is "some B is A"; we can, in addition, derive from it another, though purely formal, proposition "no A is not-B"; i.e. an E proposition. This process is called Obversion, Permutation or Immediate Inference by Privative Conception; it is applicable to every proposition including O. A further process, known as Contraposition or Conversion by Negation, consists of conversion following on obversion. Thus from "all A is B," we get "no not-B is A." In the case of the O proposition we get (by obversion) "some A is not-B" and then (by conversion) "some not-B is A" (i.e. an I proposition). In the case of the I proposition the contrapositive is impossible, as infringing the main rule of conversion. Another term, Inversion, has been used by some logicians for a still more complicated process by the alternative use of conversion and obversion, which is applicable to A and E, and results in obtaining a proposition concerning the contradictory of the original subject; thus "all A is B" becomes "some not-A is not B."
Considerable discussion has centred on the problem as to whether the process of conversion can properly be regarded as inference. The essence of inference is that the conclusion should embody knowledge which is not in the premise or premises, and many logicians have contended that no fact is stated in the converse which was not in the convertend, or, in other words, that conversion is merely a transformation or verbal change of the same statement. Hence the term Eductions and Equivalent Propositional Forms have been given to converse propositions. It is clear, for instance, that if the universal affirmative is taken connotatively as a scientific law, and not historically, no real inference is achieved by stating as another scientific fact its converse, the particular affirmative. Moreover, even if the convertend is stated as an historic fact, though there is acquired a certain new significance, it may well be argued that the inference is not immediate but syllogistic.
For this controversy see J. S. Mill, Logic, II. i. 2; Bradley, Logic, III. pt. i. chap. ii. 30-37; H. W. B. Joseph, Introduction to Logic (1906), pp. 209 foll.; J. N. Keynes, Formal Logic (3rd ed., 1894).
2. In theology, conversion (the equivalent of the Gr. ) is originally the acceptation of Christianity by heathens. It is also used generally for a change from one religion to another, or in a narrower sense for a complete change of attitude towards God, involving a deeper conviction of the ultimate religious and moral truths. Considerable difference of opinion has always existed, and still exists, within the Christian Church as to the true nature and the causes of conversion, especially in the sense last described. Some have held that man is merely the passive recipient of the Divine Grace, a view based largely on the rendering of the Authorized Version of Isaiah vi. 10 as quoted in Matt. xiii. 15, Mark iv. 12, and John xii. 40. Others again hold that baptism, as involving a second birth of the baptized person, makes subsequent conversion unnecessary or even meaningless, or conversely that conversion is this very second birth and renders baptism unnecessary. The reply generally made to such arguments is that baptism implies regeneration only, which is a change wrought from the outside by the Divine Spirit in general disposition or spiritual status, while conversion is a positive or concrete demonstration of that change, not merely the negative beginning of a new life but the positive "returning" to God in faith and repentance. The precise connexion between conversion and repentance is again a vexed question. How far and in what sense does man take an active part in his own conversion? To this it is frequently answered that while the initial stage of conversion is and can be the work of the Holy Spirit alone, it lies with man to make it complete by accepting the proffered grace in repentance and faith (cf. Acts vii. 51, "Ye stiffnecked and uncircumcised in heart and ears, ye do always resist the Holy Ghost"). A man may of his own free will avoid those surroundings which predispose him to such "resistance." The view that man cannot convert himself is clearly stated in Article X. by the Church of England. "The condition of man after the fall of Adam is such that he cannot turn (sese convertere) and prepare himself by his own natural strength and good works, to faith, and calling upon God: wherefore we have no power to do good works pleasant and acceptable to God, without the grace of God by Christ preventing us that we may have a good will, and working with us, when we have that good will." Further problems are connected with the possibility of repeated conversions of the same man, the necessity of a single strongly marked conversion completed in a single process, the significance of sudden conversion of persons in a highly emotional state, such as has been common in revivalist meetings, especially in Wales and the United States of America. Conversions of the last kind have followed frequently on striking physical phenomena, perceived in many cases only by the convert himself, such as a sudden bright light or a noise like a clap of thunder.  In all cases of conversion, however, the criterion of its validity is generally taken to be the resultant change of a man's character as manifested in his mode of life and thought, in the abstention from sin, and in devotion to good works.
3. In English law, conversion is the unauthorized exercise of dominion by one person over the property (other than money or chattels real) of another, in a manner inconsistent with his rights of possession, or the unauthorized assumption by another of the powers of the true owner of goods. The history and exact definition of this form of actionable wrong have occupied the attention of many learned writers, and the incidents of actions to assert the rights of the true owner form a considerable part of treatises on the rules and forms of civil pleading. There are many ways in which the wrong may be committed. In some cases the exercise of the dominion may amount to an act of trespass or to a crime, e.g. where the taking amounts to larceny, or fraudulent appropriation by a bailee or agent entrusted with the property of another (Larceny Acts of 1861 and 1901). But in such cases, except where money is taken, the civil remedy of the owner is by action for conversion or detention of the property, subject in the case of larceny to the rule that criminal prosecution should precede restitution by the taker. The remedy in use in these cases used to be by what was called an action on the case for trover and conversion, the plaintiff putting aside all suggestions of trespass and of crime, and resting his case on the fiction that the defendant had found and used goods not his own. The fictitious averment of loss was abolished in 1852, and under the present procedure, in which the old forms of action are not in use, the remedy is by a claim (still usually called conversion) for wrongfully depriving the true owner of personal property of its use by some specified act inconsistent with his dominion over it, usually by dealing with the property in a manner inconsistent with the owner's rights. Originally, the action of trover and conversion was limited to goods and chattels, but it is now accepted as applying to valuable securities, such as cheques and bills of exchange.
The gist of the action is in the unauthorized dealing, for however short a time and for however limited a purpose, with the personal property of another. Even refusal to deliver up to the owner is sufficient to prove conversion, though it is often made the ground of an action for detinue, if the plaintiff desires to have the property returned in specie. The knowledge, motive or good faith of the person wrongfully dealing with the property of another is for civil purposes immaterial, and the action is often brought to try the title of two claimants to the same goods; e.g. where a person who has innocently bought or taken in pledge goods stolen or illegally procured resists the claim of the original owner for the return of the goods. A warehouseman may render himself liable to the owner of goods deposited with him, through delivering the goods to a third person on a forged authority or without authority, or by issuing a warehouse receipt representing the goods to be in his possession or control when they have ceased to be so.
The exact measure of compensation due to a plaintiff whose goods have been wrongfully converted may be merely nominal if the wrong is technical and the defendant can return the goods; it may be limited to the actual damage where the goods can be returned, but the wrong is substantial; but in ordinary cases it is the full value to the owner of the goods of which he has been deprived.
Fraudulent conversion by any person to his own use (or that of persons other than the owner) of property entrusted to him is a crime in the case of custodians of property, factors, trustees under express trusts in writing (Larceny Act, 1861, ss. 77-85; Larceny Act, 1901).
The term "conversion" is also used in English law with reference to the rule of courts of equity which, in certain cases (following the maxim of treating as done what ought to have been done), treats as converted into personalty land which has been directed so to be converted by a will, contract or settlement, or as converted into land personalty which has been by such instrument directed to be applied for purchase of realty. The rule is also applied where a vendor of land dies between the making of the contract of sale and its completion by conveyance of the land. The importance of the rule lies in the different destination of realty and personalty under the laws relating to inheritance and succession.
See Bullen and Leake, Precedents of Pleading (3rd ed., 1868, 6th ed. by Dodd and Chitty, 1905); F. Pollock, on Torts (7th ed., 1904); Clerk and Lindsell, on Torts (3rd ed., 1904); Lewin, on Trusts (11th ed., 1904); Jarman, on Wills (5th ed., 1893); Dart, Vendors and Purchasers (11th ed., p. 301).
(W. F. C.)
 A term is said to be "distributed" when it is taken universally: in the proposition "men are mortal" (meaning "all men") the term "men" is "distributed" while "mortal" is undistributed, because there are mortal beings which are not men.
 Numerous instances, drawn from other religions besides Christianity, are given in Professor William James's The Varieties of Religious Experience (1902).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)