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Identity And Universals: A Conceptualist Approach to Logical, Metaphysical, and Epistemological Problems of Contemporary Identity Theory
by Carolyn Ray

Date: 11 Nov 98
Copyright: Carolyn Ray

The following is a list of terms that are used in this work. Where a proposition is intended as a real definition, the designation 'RD=' is followed by a genus/differentia definition. I only label definitions 'RD' if I think that both the term defined and the proposition correspond to something in reality, at whatever level of remove. Where the proposition is intended not as a definition but as an explanation or an informal characterization, the designation 'EX=' is used.' FICT=' is used when designating how the term is used in fictional contexts. 'ST=' indicates a stipulative use in this work, though it is not claimed that this is the only use that is justifiable with reference to reality. For explanations of terms relating to physical structure, malfunction, or disease, medical or experimental procedures, and conditions of damaged human beings, see the Appendix.

Abstract: RD= adjective: A relative term that describes a concept that denotes a group of concretes that are similar. EX= One concept can be more abstract than another; for example, ANIMAL is more abstract than MAMMAL.

Abstraction: RD= noun: A step in the process of concept formation characterized by a selective mental focus that takes out or separates a certain attribute from the concretes possessing it.

Abstraction from abstraction: RD= noun: A step in the process of concept formation characterized by a selective mental focus on the features of the concretes subsumed under two or more previously formed concepts. E.g., disregarding their dissimilarities (see measurement omission), CAT, RAT, and DOG subsume individuals that all give birth to and produce milk to feed live offspring, and these similarities give rise to the concept MAMMAL.

Analytic/synthetic dichotomy: EX= A distinction drawn between propositions in which the meaning of the predicate is contained in the subject, and all other propositions. This distinction helps to fuel many science fiction thought experiments.

A priori /A posteriori dichotomy: EX= A distinction drawn between propositions the truth of which can be known prior to experience, and those the truth of which must be determined with reference to experience.

Aristotle: A philosopher relevant to this work in that his method of objectivity is the prototype for the one used in this work. See also Locke.

Attend: RD= To focus awareness on.

Awareness: See consciousness.

Axiomatic concept: RD= A concept that identifies a fundamental fact (1) that lies at the base of all knowledge, (2) that is self-evident, (3) the proof of which must be circular since there is no knowledge prior to it, (4) the denial of which must be self-contradictory since it must assume the very concept being denied, and (5) that is present in every act of awareness. IDENTITY, EXISTENCE, and CONSCIOUSNESS are axiomatic concepts.

Bodily criterion: EX= A criterion of reidentification through time and change that takes the sameness of the physical body as justification for the judgment of sameness of person.

Borderline case: RD= A concrete that does not seem to fit precisely in either of two closely related, already-established categories, or that does not fit into a category though it has many of the characteristics of the concretes in that category.

Brain Criterion: RD= A criterion of reidentification through time and change that takes the sameness of the brain as justification for the judgment of sameness of person.

Brody, Baruch: A realist identity theorist who argues that a combination of the principle of the identity of indiscernibles and the principle of the indiscernibility of identicals is the only necessary--and the only possible--criterion of identity.

Butler, Bishop Joseph: A philosopher significant to this work because of his criticism of Locke's characterization of personal identity, which charges that Locke's memory criterion assumed what it was meant to prove or define (i.e., personal identity).

Categorize: RD= To judge that a concrete falls under a concept already formed. Contrast with abstraction.

Category: RD= A concept considered as a sorting principle.

Causal nature: RD= The ability to interact with other entities and to thereby undergo change.

Class: RD= All the referents of a concept as intended by a conscious subject. Contrast with category and group.

Classify: See categorize.

Coherent: RD= The quality of a statement, theory, or view that is internally consistent and consistent will all background knowledge.

Commissurotomy: RD= A surgical procedure to whereby the corpus callosum is cut to prevent the neural discharges associated with epilepsy from traveling between the cerebral hemispheres. (Please see Appendix C for illustrations and additional information.

Common noun: RD= A word that represents a concept that subsumes individuals (rather than the way individuals are; contrast with predicate term). See also concept.

Composition: RD= A fallacious argument that turns on the implicit false premise that whatever is true of the parts is true of the whole.

Concept: RD= A mental integration of two or more concretes on the basis of noted similarities and united by a specific definition. Contrast with group.

Concept formation: RD= The process by which universals as mind-dependent entities are brought into being by a conscious subject. See also abstraction, integration.

Conceptualism: RD= The doctrine that holds that universals are mental entities or activities that a conscious subject uses to denote concretes with noticed similarities, and that each conscious subject forms its own concepts through a process of abstraction.

Concrete: RD= noun: A unit of perception or intention that the conscious subject separates out from its background, either along real metaphysical borders or merely by attention. adjective: A relative term that describes a mental entity/activity that refers to a group of concretes that are similar. One concept is more concrete than another if all of the concretes (n) denoted by it are also grouped under a concept that subsumes additional concretes. For example, RAT is more concrete than MAMMAL.

Condition: RD= A metaphysical fact or circumstance. A necessary condition is one that must obtain for another circumstance to be possible; a sufficient condition is one that guarantees another circumstance.

Confabulation: RD= The creation of a story to explain away inconsistent or unbelievable sets of claims or facts. Commissurotomy subjects confabulate when questioned about their inconsistent responses to tests under experimental conditions.

Conscious Subject: RD= An entity that interacts with its environment through a process of impingement on its perceptual apparatus. ST= In this work, the conscious subjects usually referred to are persons.

CONSCIOUSNESS: EX= An axiomatic concept that denotes the primary fact that there is interaction with reality. The fact that this concept denotes lies at the base of all knowledge and cannot be defined without circularity; one "shows" consciousness by listing examples.

Consciousness, Divided: EX= A state of affairs in which the body is reacting to stimuli despite the fact that the person is aware of neither the stimuli nor the reaction. The condition is not necessarily well-named, since it is not clear that, e.g., commissurotomy subjects are actually conscious of two different contexts, but rather that they are aware of one while reacting automatically to the stimulus of another. See also mind, subconscious.

Consistent: RD= A statement, theory, view, attitude, or life is consistent when it admits of no contradiction.

Context: RD= The frame of reference of a given statement or definition or piece of information, in which that statement or definition can be said unqualifiedly to be true or in which a piece of information can be said to constitute knowledge. Real definitions are contextual since absolute unchanging definitions would require omniscience, which is impossible.

Context-dropping: RD= A fallacious argument that simultaneously attempts to derive its validity from a given context while ignoring some or all of the relevant essential features of the environment, circumstances, states of affairs, etc.

Contradiction: RD=An affirmation that a proposition and its negation are both true at the same time. EX= Contradictions need not be contained in any particular sentence that is uttered; if the sentence is affirmed to be true, but it negates some other true statement that could be made about the world, then a contradiction has occurred. Thus, contradictions are to be understood always with reference to reality, and only secondarily as internal linguistic inconsistency.

Counterexample: RD= A true statement about the real world that contradicts the statement(s) of a hypothesis or theory, thus showing the hypothesis or theory to be flawed or even completely false.

Counterfactual: RD= statement that describes a state of affairs that could obtain in the world, but does not. See also possibility, fiction.

Criteria: RD= A set of epistemological principles according to which judgments are made.

Criterion of identity: RD= An epistemological rule of judgment used as a guide for determining whether a single object has endured through time and change. RD= An adequate criterion of identity is one that can often be relied upon by itself, though there may be others that could be used as well.

Definition, real: RD= A proposition that indicates the wider group (genus) in which the described group of things are united with yet other similar things, and the way in which the things in the defined group differ from the other things in that group (differentia).

Definition, stipulative: RD= A proposition that indicates how the defined term will be used in a given context, regardless of whether there are other definitions and regardless of whether this use holds generally.

DIFFERENCE: RD= A concept denoting the fact that all awareness proceeds as a matter of contrasting a concrete from its background and from other concretes. See also similar.

Dimension: RD= A range of values, determined by the conscious subject or by an instrument created by the conscious subject, and measured ordinally. E.g., when one ball is "redder" than another, it is due to the fact the measurements of the wavelengths of light reflected by them fall close to each other. The range of values are determined by the conscious subject in that only certain features and certain values are available in perception to the subject, or only certain values are of interest to the subject in a given context.

Discernibility of Non-Identicals: See Leibniz's Law.

Division: RD= A fallacious argument that turns on the implicit false premise that the parts of a whole have the properties of the whole.

Dualism: EX= The metaphysical doctrine that persons (or minds, or consciousness, or souls) are distinct entities separable from bodies.

Edge: RD= The form in which metaphysical boundaries are perceived by the conscious subject.

Empiricism: EX= The epistemological theory that all knowledge is ultimately derived from experience.

Entity: See existent

Epistemological question: EX=A line of inquiry regarding how we do or can know about metaphysical reality or about mind-dependent entities, and how that knowledge is justified. See its appositional, metaphysical question.

Essence: RD= An epistemological concept denoting the quality or set of qualities that explain the rest or most of the rest of the qualities of an existent. EX= A metaphysical essence is frequently alleged to be that attribute or property that is most truly the thing, or the thing in itself, without which its identity would change (i.e., "it" would cease to exist). This work is based on the idea that, metaphysically, all of the characteristics of an entity constitute its identity, including the fact that its attributes can change.

EXISTENCE: EX= An axiomatic concept that denotes the primary factof reality. The fact that this concept denotes lies at the base of all knowledge and cannot be defined without circularity; one "shows" existence by ostention.

Existent: RD= An aspect of reality that is some way. The concept EXISTENT denotes the same concretes as the concept UNITY, but emphasizes their identity.

Experience: ST= Herein, unless otherwise qualified, a subject's active awareness of an existent or of a process.

Fact: RD= A feature of reality, as picked out by a conscious subject. EX= Some facts are more basic than all others, such as concretes. Other facts are denoted by propositions.

Fiction: ST= Any untrue story.

Figment: ST= The subject of a fictional statement or story.

Fission: RD= A process by which one entity divides into two entities both of which are like the original. One amoeba divides by fission and two amoeba result. FICT= A procedure by which one person divides, resulting in two persons.

Geach, Peter T.: A proponent of the relative identity thesis.

General term: RD=A word that represents a concept. See also common noun, predicate term.

Grelling's paradox: EX= A paradoxical puzzle generated from ill-formed propositions containing the quantifier expression, 'Whatever is true of.' E.g.: Is the phrase 'is not true of itself' true of itself. Geach rejects absolute identity on the grounds that it generates this paradox.

Group: RD= Existents considered and united through the mental effort of a conscious subject on some--but any--basis. Contrast with class.

Human being: ST= In this work, the term refers to the human body as determined by a narrow range of genetic coding as measurable by a conscious subject's perceptual apparatus, whether that body can be classified as a person or not.

I: RD= A concept denoting the conscious subject who uses it.

IDENTITY: EX= An axiomatic concept that denotes the primary fact that reality is some way. The fact that this concept denotes lies at the base of all knowledge and cannot be defined without circularity.

Identity of Indiscernibles: EX= The thesis, sometimes attributed to Leibniz, that objects that cannot be distinguished from one another "are" identical. See Leibniz's Law, Indiscernibility of Identicals.

Ignorance, appeal to: RD= A fallacious argument that turns on an implicit false premise to the effect that if x is not known to be false, then x is (or probably is, or possibly is) true. EX= In identity theory, this fallacy is committed in arguments from logical possibilism, and in also in arguments defending logical possibilism.

In re universal: EX= Realism's alleged referent of a common term that resides in the individual thing of which, in language, the common term is said to be predicated. E.g., 'rat' and 'grey' are predicated of Silhouette, in virtue of the fact that greyness and ratness reside in Silhouette. This form of realism is opposed to Platonic realism, in which the referents of common terms do not reside in individual things and yet still metaphysically cause them to be what they are.

Inconsistent: RD= The property of a proposition that contains or entails its own negation, or a set of propositions one of which negates another.

Indiscernible: RD= A judgment made about the objects of two or more experiences that the objects of those experiences cannot be distinguished from each other. EX= Sometimes taken to mean that the experiences are in fact of only one thing (see Identity of Indiscernibles).

Indiscernibility of Identicals: The thesis, sometimes attributed to Leibniz, that an object cannot be distinguished from itself. See also Leibniz's Law, Identity of Indiscernibles.

Individuation: RD= Epistemologically, the act of distinguishing one unity from another. EX= Metaphysically, those characteristics that make one thing different from another; spatio-temporal location is considered an individuating principle by many identity theorists.

Integration, mental: RD= The combination of the units of conscious attention into a single new mental entity which is used thereafter as a single unit of thought.

Intentionality: RD= The directedness or relational nature of consciousness and cognitive processes to something other than itself.

Intrinsicism: EX= A cluster of ideas including the notion that words and sentences have meaning in and of themselves without reference to a conscious subject, and that our names for things are a guide to what there really is in mind-independent metaphysical reality. For example we have the word 'dog', so that means that "there are dogs"--the implication being that there is some real property, doghood, that would exist even if no conscious subject had grouped certain objects on the basis of noted similarities.

Introspection: RD= A conscious subject's consideration of the contents of its own mind.

Justify: RD= To confirm the validity of a concept or the truth of a proposition, either by means of direct perception, or by means of inference from other concepts and propositions so confirmed. Proofs are a subcategory of justifications.

Justification (RD=) is a three-place intentional relation between a fact or proposition, a conscious subject who perceives the fact or knows the proposition to be true, and the judgment the conscious subject then forms on the basis of the fact or the proposition.

Kind: See concept.

Kolak, Daniel: An identity theorist with commitments to at least some nominalist and relativist principles.

Knowledge: RD= Awareness of facts, either through direct perceptual evidence or through propositions and reasoning ultimately based on such evidence.

Leibniz's Law: EX= (1) An epistemological principle based on that aspect or feature of reality that gives rise to the concept IDENTITY. Gottfried Leibniz's wordings of the principle (which he apparently takes as a metaphysical one) are as follows: (a) "There are never in nature two beings which are exactly alike and in which it is not possible to find an internal difference," (b) "It is not true that two substances may be exactly alike and differ only numerically," and (c) "There are no two individuals indiscernible from one another." Thus, rather than describe Leibniz's Law as the Identity of Indiscernibles, or even the Indiscernibility of Identicals, this work calls it The Discernibility of Non-Identicals. (2) A law of logical reasoning based on something like Leibniz's original statement of the principle of identity, focusing on (a) the substitutability of terms with the same referent in statements of metaphysical identity or mathematical equivalence (e.g., V=ME, V=MS, hence MS=ME), and (b) the substitutability of terms with the same referent in predicate expressions (e.g., Wa, a=b, hence Wb). This work takes Leibniz's Law to be true in both senses, arguing that sense (2) holds in all contexts as long as the context of the conscious subject is taken into account.

Locke, John: A conceptualist on whose method of analysis of concepts this work is based. Locke's alleged representationalism aside, his answers to questions of the form 'What in reality gives rise to the concept x' are neither realist nor nominalist, and shed light upon the conceptualist project of bringing the conscious subject into the analysis of concepts while acknowledging that the purpose of those concepts is to categorize the individuals of reality according to their mind-independent nature. See also Aristotle.

Logical possibilism: EX= A position with regard to reality that takes the non-self-contradictoriness of propositions as an indication that they describe possible circumstances.

Lowe, E. J.: A contemporary realist who explicitly claims that universals are ontologically on a par with individuals.

Measurement: RD= The perceptual process whereby the features of mind-independent objects are compared either to each other or to the conscious subject itself. E.g., the judgment "These objects are the same shade of brown" is made possible by the visual measurement of the wavelength of light reflected off the objects' surfaces.

Measurement omission: RD= The step in concept formation whereby the variations between objects of perception are disregarded for the purpose of focusing on and integrating their similarities in measurement.

Memory: RD= Discrete instances of awareness of past events. Also, a type of abstraction that relates awareness of past events to the conscious subject and its present environment and experiences.

Memory criterion: EX= A criterion of reidentification that takes sameness of memories as justification for judgment of sameness of person.

Mental entity: ST= A mind -dependent process, which is only an entity by metaphorical extension, such as a concept or a proposition.

Mental state: ST= Primarily, those internal states to which each person has exclusive conscious access; derivatively includes those internal states to which a person does not have direct private access.

Metaphysical boundary: RD= An aspect of reality that gives rise to perceivable differences.

Metaphysical question: EX= A line of inquiry regarding the actual mind-independent nature of an entity, as opposed to what we can or do know about the entity and how we come to know it and how we can justify claims about it. See appositional, epistemological question.

Mind: RD= The capacity to process information, consciously or subconsciously. EX= Mind includes consciousness but is not identical to it. On this definition, HM, dogs, and babies have minds. "Divided mind" refers to the commonplace fact that information is being processed with varying degrees of consciousness or attention by a single mind; it is this fact, especially in the exaggerated form it takes in split-brain patients and those suffering multiple personality syndrome, that inspires the unwarranted conclusion that there might be more than one mind associated with one body.

Multiple occupancy thesis: EX= The metaphysical doctrine that there are or could potentially be more than one consciousness associated with a particular body or brain.

Multiple personality syndrome: EX= A psychological condition characterized by a single person exhibiting different sets of personality traits at different times, often without being aware of the changes when they happen or even of the existence of such changes or their nature. A person suffering from this condition is sometimes described by friends and acquaintances as being like several different persons inhabiting the same body. See also multiple occupancy thesis.

Natural kind: RD= A concept denoting objects that occur without the direction of human beings but among which similarities are observed. EX= For realism, a natural kind is a metaphysical essence; for conceptualism, a natural kind is a concept.

Natural Realism: Also called 'direct realism'. EX= An epistemological position characterized by a commitment to a mind-independent reality and the ability of conscious subjects to be directly aware of that reality through perceptual apparatus.

Necessary condition: RD= A metaphysical circumstance the existence of which is required for the existence or expression or possibility of other metaphysical features or for the successful operation of epistemological functions such as concept formation. Necessary conditions can be understood in an epistemological sense, in that one kind of knowledge is necessary for another; but the risk of equivocation requires that great care be taken in doing so.

Nominalism, extreme: EX= The position with regard to universals that takes the linguistic general term itself to be the only thing similar about the things to which the term refers. Implicit concessions to at least some premises of extreme nominalism are the basis for logical possibilism.

Noonan, Harold: EX= An identity theorist who shows commitments to some realist doctrines and possibly some dualist premises, and who focuses on metaphysics to the explicit exclusion of epistemology.

Objective: RD= The property of a concept or of a claim that accounts for the conscious subject's interaction with the object of awareness.

Objectivity, Method of : RD=The method of analyzing and clarifying a concept by asking the question, "What--if any--are the facts of reality that give rise to this concept?"

Onus of proof: RD= The responsibility for providing evidence that claim is true. EX= This burden is on the person who makes the claim, and cannot legitimately be shifted to an adversary. For example, the onus of proof is on a person who asserts the possibility of brain transplants as a counterexample to any theory of personal identity; the person whose theory it is has no responsibility to try to disprove the possibility of brain transplants in order to defend his theory from it (see also counterexample, science fiction, and appeal to ignorance).

Parfit, Derek: A widely-admired "identity theorist" whose principle metaphysical conclusion is that persons are not what we think we are, from which he draws the ethical conclusion that personal identity is not what matters--or, if it is, that we should believe that it is not what matters. Parfit originally inspired me to coin the term 'sci-fi philosopher.'

Perception: RD=An integrative but non-conceptual form of knowledge whereby we resolve sense data.

Persistence: RD= The existence of an individual through time and change.

Person: RD=A living human being with a mind capable of memory, abstraction, environmental interaction, and causal efficacy with respect to bodily and psychological attributes, and persistent self-awareness with regard to all of these activities and traits.

Personality: RD= The format in which a conscious being responds to its environment, manifested in behavior.

Physical criterion: See bodily criterion. EX= The physical criterion is stated by some personal identity theorists as a metaphysical condition that suffices for and/or necessitates the persistence of a person, that condition being "enough of a brain to be the brain of a living person."

Possibility: Primarily, a description of the state of a conscious subject regarding a conjecture and the evidence for it--some evidence has been collected, but the conjecture has not been established in the mind of the claimant. By metaphorical extension, an alleged state of affairs which, given the laws operative in reality and the nature of the things that are part of that state of affairs, might come to be. All actual states of affairs are possibilities, and non-actual states of affairs that accord with the laws and causal properties of the things described are also possibilities. Note: The contradictoriness of two propositions shows that those two propositions describe states of affairs that cannot possibly coexist; but the non-contradictoriness of two propositions tells us nothing about the possibility of the states of affairs described.

Predicate term: RD= A word that refers to concretes selected on the basis of one particular way that they are (rather than focusing on the individual--contrast with common noun).

Primary fact: RD= A fact which is not analyzable in terms of other facts or concepts, that lies at the base of and is implicit in all knowledge. There is no knowledge prior to primary facts, such that evidence could be cited in the proof of them without circularity.

Proof: RD= Process of justification by which a conscious subject establishes the correspondence between its ideas and the facts of reality by deriving a proposition from other already established propositions.

Property: RD=One aspect of a concrete as singled out by a conscious subject.

Proprioception: RD= The sensation of the position of the various parts of a conscious subject's body.

Psychological criterion: EX= An epistemological principle for the reidentification of person on the basis of the contents of its mind.

Realism: RD= With regard to particulars, the doctrine that reality is mind-independent, and that consciousness is passive, unable to create its own contents, and must conform to it in order to have knowledge. With regard to universals, moderate realism is the doctrine that universals exist in the things they are said of; platonic realism is the doctrine that universals exist separate from the things they inform .

Reductio ad absurdum: RD= An argument that proceeds to the falsehood of a proposition by assuming the proposition and then showing that a contradiction follows from it.

Reference: RD= A three-place relation between the conscious subject, a concept, and the existents which have been integrated under the concept; or between the subject, a name or description, and a particular. Reference fails (i.e., though attempted, is not successful) when no such object(s) exist(s). Reference does not occur at all in the absence of a conscious subject (e.g., printed words do not refer by themselves; a conscious subject refers to existents by means of the concepts, names, or descriptions which words represent).

Reidentification: RD= An epistemological concept referring to the act of a subject picking out at different times the same object.

Relative identity thesis: EX= The thesis that identity is not absolute and that Leibniz's Law does not hold in at least some contexts such that individuals a and b can both fall under concepts F and G, and a is the same F as b but not the same G as b, even though F's are just G's. In this form it is presented by Peter Geach.

Relation: RD= An epistemological concept referring to "a way of comparing or considering two things together" (following Locke, Essay, II, xxv, 7).

Resemblance: See similarity.

Russell, Bertrand: A philosopher/logician of many talents and varying ontological commitments with regard to universals, whose tendency to eliminate the conscious subject from the analysis of propositions solved many puzzles while creating many beings and removing meaning from many terms.

SAME: EX= See also similar. (1) A concept that denotes identity and persistence. (2) A concept that denotes the fact that two independent existents can be subsumed under one mental category in virtue of their similarity (as in, 'This dot is the same color red as that one').

Science Fiction: RD= Stories that include reference to technology (which usually remains unspecified so that narrative flow is not impeded) as a central theme. ST= Sci-fi philosophers believe that science fiction is useful for rearranging our conceptual scheme. See also logical possibilism.

SELF: RD= A concept that denotes the subject who uses it. EX= SELF is a universal in that, by extension, the conscious subject understands that the word 'self' is used similarly by all conscious subject, and thus can be used to talk about all such entities.

Self-evident: EX= Given in experience, known without appeal or reference to prior knowledge or to reasoning. See also primary fact.

Shoemaker, Sydney: A dualist identity theorist.

SIMILARITY: RD= An intentional relation between a conscious subject and two or more things that are close in measurement along some dimension(s). Early understanding of similarity comes as a result of perceptual information, but higher-level concepts themselves can be compared and said to be similar on the basis that the facts they subsume are similar.

Sortal: EX= In conceptualism, a sortal is a concept. For some theories of universals, a sortal is a real existent; for others, it is a convention.

Sortally relative: EX=Conceptualism takes identity to be sortally relative in the sense that (1) the properties of an existent are part of its identity, and (2) 'x is identical to y' is an incomplete expression, which must be parsed as 'x is the same F as y'. Contrast with relative identity thesis.

Split-brain: EX= A human brain upon which a commissurotomy has been performed. Personal identity theorists sometimes use the term to mean that there is divided consciousness, but this is a conflation of an actual state of affairs and unfounded speculation.

Stimulus Chimera: EX= An image composed of the left half of one picture and the right half of another; for example, the left half of a picture of a woman and the right half of a picture of a child. These images are used to test immediate communication between the cerebral hemispheres of commissurotomy subjects.

Stolen concept: RD= A fallacious argument or false statement that presumes or uses a valid concept in order to deny the validity of that very concept.

Subconscious process: RD= A mental process in which the mind engages without the conscious subject's attention.

Sufficient condition: RD= A metaphysical fact that guarantees the existence or occurrence of another metaphysical fact.

Thing: RD= A broad, higher-level abstract concept that serves as a variable or placeholder in a proposition where some concrete (but any concrete, in a given range of alternatives) may be filled in. The concept THING is vague, and formed on the basis of many lower-level concepts. See also existent.

Thought experiment: RD= A description of an actual state of affairs, or of a counterfactual state of affairs. Certain measurements are omitted in order to focus attention on one or a few particular features of the situation described. The omitted measurements are not ignored, but abstracted away from for the moment. No attempt is made to deny the importance and causal efficacy of those measurements in the actual situation, and the experiment is not complete until the measurements are reintroduced, thus providing the link between the conclusions, drawn within the confines of the experiment, and reality.

Undeniable Fact: RD= A fact affirmed in any attempt at proof or disproof of that fact.

Unit: RD= A member of a group of similar members attended to by a conscious subject as standing in certain relationships. E.g., a length of rope can be a unit of comparison for other lengths.

Unity: RD= An aspect of reality that is separated from its background by metaphysical boundaries. The concept UNITY denotes the same concretes as the concept EXISTENT but emphasizes their boundaries.

Universal: See concept.

Wilkes, Kathleen: EX= A personal identity theorist who defends the thesis that personal identity theory should be conducted without thought experiments.

Williams, Bernard: EX= A personal identity theorist who defends the epistemological thesis that reidentification of persons is always ultimately done through reidentification of human bodies. His arguments answering sci-fi identity theorists' and dualists' arguments to the contrary often take the form of the now-notoriously misinterpreted and misquoted Reduplication Argument.

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