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Topic: Obversion

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	Obversion - Wikipedia, the free encyclopedia
		In traditional logic, obversion is a form of immediate inference in which from a given categorical proposition another proposition is inferred which has as its subject the original subject, and has as its predicate the complement of the original predicate.
		In the obversion of a particular negative to a particular affirmative the quantity of the subject also remains unchanged, and the predicate term is changed from simple negation to a term of the complementary class.
		In addition, obversion allows us to navigate through the traditional square of logical opposition by providing a means for us to proceed from "A" Propositions to "E" Propositions, as well as from "I" Propositions to "O" Propositions, and vice versa.
	en.wikipedia.org /wiki/Obversion (452 words)

	Conversion, Obversion, And Contraposition
		When you apply the logical operations - conversion, obversion, and contraposition - to categorical propositions, you yield new categorical propositions that are sometimes valid (logically equivalent) and sometimes not valid (not logically equivalent).
		The result of obversion is called the obverse of the original proposition to which it is applied.
		Obversion (valid for A, E, I, and O) Changes the quality of the prediate and the quality of the statement as a whole.
	campus.murraystate.edu /academic/faculty/franklin.robinson/2ConversionObversionContraposition.htm (792 words)

	Obversion Definition / Obversion Research (Site not responding. Last check: 2007-10-11)
		In traditional logic Obversion is a form of immediate inferenceTo infer is to draw a conclusion based on what one already knows and on that alone.
		obversion is the inference from a categorical statement to its obverse.
		Obversion is the only immediate inference that is valid for categorical propositions of every form.
	www.elresearch.com /Obversion (220 words)

	[No title]
		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.
		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.
		In the case of the I proposition the contrapositive is impossible, as infringing the main rule of conversion.
	encyclopedia.jrank.org /correction/edit?locale=en&content_id=17388 (1621 words)

	Contraposition - Wikipedia, the free encyclopedia
		The contrapositive of the original proposition is then derived by conversion to another 'E' type proposition,
		The process is completed by further obversion resulting in the 'A' type proposition that is the obverted contrapositive of the original proposition,
		The successive applications of conversion and obversion within the process of contraposition may be given by a variety of names.
	en.wikipedia.org /wiki/Contraposition (648 words)

	immediate inferences
		Obversion consists of a process of retaining the quantity of the proposition, but the quality must change since the thing or quality that is predicated of the subject has received a negative prefix.
		Using conversion and obversion, the reason that the E form will not contrapose should be clear.
		Since the A form cannot be converted, the complementary class appearing in the subject position cannot be moved to the predicate position in order to apply obversion again.
	pegasus.cc.ucf.edu /~stanlick/immedinf.html (1537 words)

	LESSON # 13
		The three operations used to accomplish this translation are conversion, obversion, and contraposition.
		To determine the complement of a term you need to make it into the "opposite" term, or rather, into the class of things that is outside the class of the original term.
		Use conversion, obversion and contraposition to determine whether the following arguments are valid or invalid.
	www.uky.edu /~rosdatte/phi120/lesson13a.htm (921 words)

	Further Immediate Inferences
		Obversion: changing the quality and replacing the predicate term with its complementary class (valid, or preserves truth value for all propositions--the A, E, I, and O).
		Notice that contraposition is the same thing as successive obversion, conversion, and obversion of a proposition.
		Again for contraposition, as for obversion, one has to be careful about describing the class complement for exactness.
	philosophy.lander.edu /logic/further.html (1450 words)

	Square of Opposition
		Certain additional principles ("contraposition" and "obversion") were sometimes adopted along with the Square, and they genuinely yielded inconsistency.
		They were permitted in the theory, the O form definitely did not have existential import, and the logical theory, stripped of the incorrect special cases of contraposition and obversion, was coherent and immune to 20th century criticism.
		In the twentieth century Lukasiewicz also developed a version of syllogistic that depends explicitly on the absence of empty terms; he attributed the system to Aristotle, thus helping to foster the tradition according to which the ancients were unaware of empty terms.
	www.science.uva.nl /~seop/archives/fall1999/entries/square (4426 words)

	LESSON # 18
		Obversion gives you the term compliment of the P term only, if that's what you want.
		Obversion plus Contraposition in that order, changes the S term of the original proposition, if you start with an A or O. Once you have finished your operations, and have three identical terms, each used twice, Check to make sure that the
		If you performed conversion or obversion on the conclusion, you might have to switch their order as a final step to put the syllogism into standard form, even if they were in the correct order to begin with.
	www.uky.edu /~rosdatte/phi120/lesson18a.htm (500 words)

	DOLHENTY ARCHIVE: The Opposition of Propositions
		Eduction is a mental process whereby, from any proposition taken as true, we derive another proposition implied in it, though differing from the first proposition in subject or predicate or both.
		Obversion is an eduction in which the inferred judgment, while retaining the original subject, has for its predicate the contradictory of the original predicate.
		Conversion is unlike obversion because not every standard sentence has an equivalent converse.
	radicalacademy.com /logicoppofprop2.htm (1124 words)

	[No title]
		After the first step, the standard form is Some C are non-R. After the second step, the standard form of the minor premise is Some C are not R. The conclusion is also an I proposition, so again the operations of conversion and obversion may yield logically equivalent statements.
		The standard form of the conclusion is now Some C are not S. Using the reduced terms for the minor premise and conclusion, rewrite the standard form of this syllogism.
		After the first step, the standard form is No S are non-W. After the second step, the standard form of the conclusion is All S are W. Using the reduced terms for the minor premise and conclusion, rewrite the standard form of this syllogism.
	a-s.clayton.edu /walkup/CRIT/ch.5.4key.doc (564 words)

	Dr Smith's Logic Page
		The operations of conversion, obversion, and contraposition are applied to categorical propositions to yield new categorical propositions - these can become immediate arguments.
		So, an obversion is a proposition makes a reference to this complimentary class, in a negative fashion.
		We create an obversion by changing the quality of the proposition (from affirmative to negative, or vice versa) and then negating the predicate term.
	www.candleinthedark.com /aristotlelogic.html (1453 words)

	AIP Introduction to Logic: Chapter 4 (Site not responding. Last check: 2007-10-11)
		If you are having difficulty understanding the lecture notes, please review the process for testing arguments using both the Modern Square of Opposition and Venn Diagrams.
		Determine which of the three new moves: conversion, contraposition or obversion has taken place between the premise and conclusion of the argument.
		If only one term is to be changed to its complement, then it is likely that you will use obversion along the way.
	www.thinkingshop.com /AIP/logic/chap4smartbd.htm (571 words)

	categorical propositions (Site not responding. Last check: 2007-10-11)
		Three important immediate inferences deal with the logical relationships of conversion, obversion and contraposition (you may recall these terms from high school geometry class).
		Conversion is legitimate for E and I propositions, but not for A and O propositions.
		Obversion involves making two changes: the quality is changed (either from affirmative to negative or negative to affirmative) and the compliment of the predicate class is substituted for the predicate term.
	cstl-cla.semo.edu /hill/PL120/notes/categorical_propositions.htm (1550 words)

	Mulder, Existential Assumptions of Traditional Logic
		Abstract: There have been and continue to be disagreements about how to consider the traditional square of opposition and the traditional inferences of obversion, conversion, contraposition, and inversion from the perspective of contemporary quantificational logic.
		There has been and continues to be widespread disagreement about how best to regard this aspect of Traditional logic (and related inferences in syllogistic logic) in light of these criticisms from contemporary logicians.
		There is strong evidence that Aristotle did not regard obversion as an equivalence relation and even some indication that he did not think of contraposition as we commonly do today (on this latter point see Church's comments on Lukasiewicz in his 1965, pp.
	home.att.net /~profmulder/EATL.htm (7354 words)

	Obversion (Site not responding. Last check: 2007-10-11)
		Please look for Obversion, Demorgan and Demorgan's Law to find more Obversion information.
		Obversion of an A How to do it.
		Obversion a relation between propositions (or sentences) definition—the obverse of a...
	www.obversion.info (190 words)

	[No title]
		Standard form of premise: Some G are non-B. False I-proposition Obversion of premise: Some G are not B. False O-proposition Subcontrary of previous line: Some G are B. True I-proposition [With the subcontrary relation, at least one proposition must be true.
		Since the O-proposition on the preceding line is false, this I-proposition must be true.] Standard form of conclusion: Some B are G. True I-proposition Conversion is the operation performed with the statement on the subcontrary line that leads to the conclusion.
		Obversion of previous line: () Is it true or false?
	a-s.clayton.edu /walkup/CRIT/ch.4.5akey.doc (434 words)

	Week3/1
		It is essential to know something about classes in order to understand obversion as a type of immediate inference, since obversion depends on the notion of "complement" to the class designated by the predicate term.
		These two 'nons' negate their corresponding classes but as such they have nothing at all to do with the QUALITY of the statement, which is a characteristic of the statement as a whole.
		A contrapositive can be formed for all types of categorical statements; it is valid for A and O propositions, but not for E and I ones.
	condor.depaul.edu /~mlarrabe/wk3a.htm (1665 words)

	'Statements & Implications' from 'Deduction' in 'Clear Thinking'
		This form of the original proposition (1) is called the obverse, and the process of change is called obversion: in 2 we are, as it were, looking at 1 from a different point of view.
		But in changing from the affirmative to the negative form of a proposition, or vice versa, it is very easy to fall into the error or fallacy known as illicit obversion and to draw unwarrantable conclusions.
		There is another process called conversion, by which the subject and the complement of certain propositions may be interchanged: e.g.
	www.ourcivilisation.com /smartboard/shop/jepsonrw/chap81.htm (1332 words)

	Fa?
		Notice how I’ve used obversion to change the universal affirmative sentence to a universal negative sentence.
		Obversion is the process whereby one can obtain an affirmative from the negation of a negation, e.g., So~P to SiP, or “Some S is not non-P” to “Some S is P.” (This is similar to the multiplying of two negative numbers to obtain a positive number in mathematics.)
		First, we can try the obversion of XiM, which is Xo~M. That will certainly polarize the middle terms.
	vernerable.tripod.com /logicalalgebra1.htm (2535 words)

	Clarion-Venango Logic & Inquiry: Chapter 4
		Review the diagrams to be sure you understand the relation being expressed.
		Obversion is a move that allows us to switch the quality and predicate terms for all four statements: A, E, I and O. When is it a legal move?
		Obversion can be used on A, E I and O statements.
	www.thinkingshop.com /Clarion/logic/chap4.htm (2176 words)

	The Logical Fallacies: Using the Categorical Converter - 6
		We continue by tracing our path from the PnS under the O column to the PS under the A column.
		Moving from PnS to PS follows the rule of Obversion.
		"All non-S is non-P" is true, thus (by obversion) "No non-S is P" is true, thus (by conversion) "No non-P is non-S" is true, thus (by obversion) "All P is S" is true.
	onegoodmove.org /fallacy/use5.htm (93 words)

	Aristotles logic decidable? (Site not responding. Last check: 2007-10-11)
		and I didn't see obversion included among the rules.
		Obversion does not belong to the kernel of Aristotelian logic, because
		predicate logic - then, of course, obversion rules should be valid.
	www.groupsrv.com /science/about84390-0-asc-45.html (4515 words)

	obvoluted obvoluted obversant Obversant - definition of Obversant by the Free ... (Site not responding. Last check: 2007-10-11)
		Why We See Three-Dimensional Objects: Another Approach A failure in the gradient descent resulted in a tangled figure that often contained obvoluted, non-planar faces see Figure 1, Examples of Tangles This was by far the most common problem with the
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	hyperlipidemia.host2.ranusa.com /1141046489.html (644 words)

	Using Immediate Inferences
		Some P are not M. No nonM are S. ==== Obversion ===>
		All M are S. No S are P. No S are P. All nonM are P. The easiest thing to do here is use nonM as the middle term!
		Or: Use obversion on the second premise (nonM will remain in the first premise).
	www.public.coe.edu /~pmccormi/phl115/s02/exercises/using_immediate_inferences.solutions.html (243 words)

	Definition of obversion - Merriam-Webster Online Dictionary (Site not responding. Last check: 2007-10-11)
		Click here to search for another word in the Merriam-Webster Online Dictionary.
		For More Information on "obversion " go to Britannica.com
		Get the Top 10 Search Results for "obversion "
	www.bonus.com /contour/merriam_webster/http@@/www.m-w.com/dictionary/obversion (56 words)

	Sophia on the web: Logic Page ~ Inference chains with Universal Categorical Propositions
		Using the rules of obversion, conversion, and conversion by limitations we can construct inference chains.
		The chains branch out without duplicating existing links.
		Branches happen after a CL and begin with C. Chains begin with one of each operation (obversion and conversion) and alternate (using CL on the A statements) until the end is reached.
	members.aol.com /moresophia/topic17.html (166 words)

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