00100			 EXPLANATIONS AND MODELS
00200	 The Nature of Explanation
00300		It is perhaps as difficult to explain explanation  itself  as
00400	it is to explain anything else. (Nothing, except everything, explains
00500	anything). The explanatory practices  of  different  sciences  differ
00600	widely  but  all  share the purpose of someone attempting to answer a
00700	why-how-what-etc.    question  about  a  situation,  event,  episode,
00800	object or phenomenon.  Thus scientific explanation implies a dialogue
00900	whose participants share some interests, beliefs,  and  values.  Some
01000	consensus  must  exist  about  what  are  admissible  and appropriate
01100	questions and answers.    The participants must have some  degree  of
01200	agreement  on  what  is a sound and reasonable question and what is a
01300	relevant, intelligible, and (believed) correct answer. The  explainer
01400	tries  to satisfy the questioner's curiosity by making comprehensible
01500	why something is the way it is.   Depending  on  what  mystifies  the
01600	questioner,the  answer  may be a definition, an example, a synonym, a
01700	story, a theory, a model-description, etc.  The  answer  attempts  to
01800	satisfy  curiosity  by  settling  belief, at least temporarily, since
01900	scientific  beliefs  are  corrigible  and  revisable.   A  scientific
02000	explanation  aims  at  convergence  of  belief in the relevant expert
02100	community.
02200		Suppose a man dies and a questioner (Q) asks an explainer (E): 
02300		Q: Why  did  the  man  die?  
02400	One answer might be:
02500		E: Because he swallowed  cyanide.
02600	This explanation might be sufficient to satisfy Q's curiosity and  he
02700	and he stops asking further questions. Or he might continue:
02800	        Q. Why did the cyanide kill him?
02900	and E replies:
03000	        E: Anyone who swallows  cyanide dies.
03100	This explanation appeals to a universal generalization under which is
03200	subsumed the  particular  fact  of  this  man's  death.   Subsumptive
03300	explanations,  however,  satisfy some questioners but not others who,
03400	for example, might want to know about  the  physiological  mechanisms
03500	involved.
03600	        Q: How does cyanide work in causing death?
03700	        E: It stops respiration so the person dies from lack of oxygen.
03800		If Q has biochemical interests he might inquire further: 
03900		Q:What is cyanide's mechanism of drug action on the
04000		respiratory center?
04100		The last two questions refer to causes. When human action  is
04200	to  be  explained,  confusion  easily  arises  between  appealing  to
04300	physical, mechanical causes and appealing to  symbolic-level  reasons
04400	which   constitute  learned,  acquired  strategies  seemingly  of  an
04500	ontological order different from causes. (See Toulmin, 1971).
04600		The phenomena of the paranoid mode can  be  found  associated
04700	with  a  variety  of  physical  disorders.     For  example, paranoid
04800	thinking   can   be   found   in   patients   with   head   injuries,
04900	hyperthyroidism,  hypothyroidism, uremia, pernicious anemia, cerebral
05000	arteriosclerosis, congestive heart  failure,  malaria,  epilepsy  and
05100	drug  intoxications  caused  by  alcohol, amphetamines, marihuana and
05200	LSD. In these cases the paranoid mode is not a primary disorder but a
05300	disorder  in  processing  information secondary to another underlying
05400	disorder. To account for the association  of  paranoid  thought  with
05500	these  physical  states of illness, a psychological theorist might be
05600	tempted to  hypothesize  that  a  purposive  cognitive  system  would
05700	attempt  to  explain ill health by attributing it to other malevolent
05800	human agents. But before making such an  explanatory  move,  we  must
05900	consider  the at-times elusive distinction between reasons and causes
06000	in explanations of human behavior.
06100		One  view  of  the  association  of  the  paranoid  mode with
06200	physical disorders might be that the physical illness  simply  causes
06300	the  paranoia,  through  some  unknown mechanism, at a physical level
06400	beyond the influence of deliberate self-direction and self-control.
06500	That  is,  the  resultant  paranoid  mode  represents  something that
06600	happens to a person as victim, not  something  that  he  does  as  an
06700	active  agent.   Mechanical causes thus provide one type of reason in
06800	explaining behavior. 
06900		Another  view  is  that the paranoid mode can be explained in
07000	terms of symbolically-represented reasons  consisting  of  rules  and
07100	patterns  of  rules  which specify an agent's intentions and beliefs.
07200	In a given situation does a person as an agent recognize, monitor and
07300	control  what  he is doing or trying to do?    Or does it just happen
07400	to him automatically without conscious deliberation?
07500		This  question  raises a third view, namely that unrecognized
07600	symbolic-structure reasons, aspects of  the  symbolic  representation
07700	which  are sealed off from reflective deliberation, can function like
07800	mechanical causes in that they are inaccessible to voluntary control.
07900	If  they  can be brought to consciousness, such reasons can sometimes
08000	be modified voluntarily by the agent, who, using ordinary language as
08100	its  own  metalanguage, can reflexively talk to and instruct himself.
08200	This second-order monitoring and control through  language  contrasts
08300	with  an  agent's  inability  to modify mechanical causes or symbolic
08400	reasons  which  lie  beyond  the  influence  of  self-criticism   and
08500	self-emancipation   carried   out   through  linguistically  mediated
08600	argumentation.     Timeworn conundrums about concepts  of  free-will,
08700	determinism,  responsibility,  consciousness and the powers of mental
08800	action here plague us unless we can  take  advantage  of  a  computer
08900	analogy  in  which  a  clear  and useful distinction is drawn between
09000	levels of mechanical hardware and symbolically-represented  programs.
09100	This important distinction will be elaborated shortly.
09200	
09300		Each of these three views provides a serviceable  perspective
09400	depending on how a disorder is to be explained and corrected.    When
09500	paranoid processes occur during amphetamine intoxication, they can be
09600	viewed  as  biochemically  caused and beyond the patient's ability to
09700	control volitionally through internal self-correcting dialogues. When
09800	a  paranoid  moment  occurs  in  a normal person, it can be viewed as
09900	involving   a   symbolic   misinterpretation.     If   the   paranoid
10000	misinterpretation  is  recognized as unjustified, a normal person has
10100	the emancipatory power  to  revise  or  reject  it  through  internal
10200	dialogue.  Between these extremes of drug-induced paranoid states and
10300	the self-correctable paranoid moments of the normal person, lie cases
10400	of  paranoid  personalities, paranoid reactions and the paranoid mode
10500	associated   with   the   major    psychoses    (schizophrenic    and
10600	manic-depressive).
10700		One opinion has it that the major psychoses are a consequence
10800	of  unknown  physical  causes  and  are, therefore, beyond deliberate
10900	voluntary control.   But what  are  we  to  conclude  about  paranoid
11000	personalities  and  paranoid  reactions  where no physical "hardware"
11100	disorder  is  detectable  or  suspected?   Are  such  persons  to  be
11200	considered  patients  to  whom something is mechanically happening at
11300	the physical level or are they agents whose behavior is a consequence
11400	of  what  they do at the symbolic level?   Or are they both agent and
11500	patient depending on how one views the  self-modifiability  of  their
11600	symbolic  processing?    In  these perplexing cases we shall take the
11700	position that in  normal,  neurotic  and  characterological  paranoid
11800	modes,  the psychopathlogy represents something that happens to a man
11900	as  a  consequence  of  what  he  has  experientially  undergone,  of
12000	something  he now does, and something he now undergoes.    Thus he is
12100	both agent and victim whose symbolic processes have powers to do  and
12200	liabilities  to undergo.  His liabilities are reflexive in that he is
12300	both victim of, and can succumb to, his own symbolic structures.
12400	
12500		From  this  standpoint  I  would  postulate  a duality at the
12600	symbolic level between reasons and causes.  That  is,  a  consciously
12700	unrecognized reason can operate like a mechanical cause in that it is
12800	inaccessible to voluntary modification by symbolic reprogramming.  It
12900	is not reasons themselves which operate as causes but their execution
13000	which serves as a determinant of behavior.  Human  symbolic  behavior
13100	is   non-determinate   to   the   extent   that  it  is  autonomously
13200	self-determinate. Thus the power to  select  among  alternatives,  to
13300	make  some decisions freely and to change one's mind is non-illusory.
13400	When a reason is recognized to function as a cause and is  accessible
13500	to  self-monitoring (the monitoring of monitoring), emancipation from
13600	it can occur through change or rejection of belief. In this sense  an
13700	at    least    two-levelled    system    is    self-changeable    and
13800	self-emancipatory, within limits.
13900		Explanations  both  in  terms  of  causes  and reasons can be
14000	indefinitely extended and endless questions  can  be  asked  at  each
14100	level of analysis.  Just as the participants in explanatory dialogues
14200	decide what is taken to be problematic, so they  also  determine  the
14300	termini  for a series of questions and answers.   Each discipline has
14400	its characteristic stopping points and boundaries.
14500		Underlying such explanatory dialogues are larger and  smaller
14600	constellations   of   concepts   which   are  taken  for  granted  as
14700	nonproblematic background.    Hence in considering the strategies  of
14800	the paranoid mode "it goes without saying" that any living teleonomic
14900	system ,as the larger constellation ,  strives  for  maintenance  and
15000	expansion  of life. Also it should go without saying that, at a lower
15100	level, ion transport takes place through nerve-cell membranes.  Every
15200	function  of  an  organism  can  be viewed as governing a subfunction
15300	beneath and depending on a transfunction above which  calls  it  into
15400	play for a purpose.
15500		There are many alternative ways of explaining just  as  there
15600	are many alternative ways of describing.  An explanation is geared to
15700	some  level  of  what  the  dialogue  participants  take  to  be  the
15800	fundamental  structures  and processes under consideration.  Since in
15900	psychiatry   we   cope   with   patients'   problems   using   mainly
16000	symbolic-conceptual  techniques,(it is true that the pill, the knife,
16100	and electricity are also available), we are interested in aspects  of
16200	human  conduct  which can be explained, understood, and modified at a
16300	symbol-processing level.   Psychiatrists  need  theoretical  symbolic
16400	systems from which their clinical experience can be logically derived
16500	to interpret the case histories of their patients. Otherwise they are
16600	faced  with  mountains  of  indigestible  data  and  dross.  To quote
16700	Einstein: "Science is an attempt to make the chaotic diversity of our
16800	sense  experience correspond to a logically uniform system of thought
16900	by correlating single experiences with the theoretic structure."
17000	
17100	 The Symbol Processing Viewpoint
17200	
17300		Segments  and sequences of human behavior can be studied from
17400	many perspectives.    I shall view  sequences  of  paranoid  symbolic
17500	behavior  from  an information-processing standpoint in which persons
17600	are viewed as symbol users.  For  a  more  complete  explication  and
17700	justification  of this perspective , see Newell (1973) and Newell and
17800	Simon (1972).
17900		In brief, from this vantage point we  define  information  as
18000	knowledge   in   a  symbolic  code.  Symbols  are  considered  to  be
18100	representations  of  experience  classified   as   objects,   events,
18200	situations and relations. A symbolic process is a symbol-manipulating
18300	activity posited to account for observable symbolic behavior such  as
18400	linguistic  interaction. Under the term "symbol-processing" I include
18500	the seeking, manipulating and generating of symbols.
18600		Symbol-processing   explanations   postulate   an  underlying
18700	structure  of  hypothetical  processes,  functions,  strategies,   or
18800	directed  symbol-manipulating procedures, having the power to produce
18900	and being responsible for observable patterns of  phenomena.  Such  a
19000	structure  offers an ethogenic (ethos = conduct or character, genic =
19100	generating)  explanation  for  sequences  or  segments  of   symbolic
19200	behavior.  (See Harre and Secord,1972).  From an ethogenic viewpoint,
19300	we can posit processes, functions, procedures and strategies as being
19400	responsible  for  and  having  the  power  to  generate  the symbolic
19500	patterns  and  sequences  characteristic  of   the   paranoid   mode.
19600	"Strategies"  is  perhaps the best general term since it implies ways
19700	of obtaining an objective - ways which have suppleness and pliability
19800	since choice of application depends on circumstances.        However,
19900	I shall use all these terms interchangeably.
20000	
20100	 Symbolic Models
20200		Theories  and  models  share  many  functions  and  are often
20300	considered equivalent.   One important distinction, however, lies  in
20400	the  fact  that a theory states a subject has a certain structure but
20500	does not exhibit that structure in itself. (See Kaplan,1964). In  the
20600	case  of  computer  simulation  models  there exists a further useful
20700	distinction. Computer simulation models which  have  the  ability  to
20800	converse  in natural language using teletypes, actualize or realize a
20900	theory in the form of a dialogue algorithm. In contrast to a  verbal,
21000	pictorial  or  mathematical representation, such a model, as a result
21100	of interaction, changes its states over time and ends up in  a  state
21200	different from its initial state.
21300		Einstein once remarked, in contrasting the act of description
21400	with  what  is  described,  that it is not the function of science to
21500	give the taste of the soup.  Today  this  view  would  be  considered
21600	unnecessarily  restrictive.   For example, a major test for synthetic
21700	insulin is whether it reproduces the effects, or at least some of the
21800	effects  (such  as  lowering  blood sugar), shown by natural insulin.
21900	Similarly, to test whether a simulation is  successful,  its  effects
22000	must  be compared with the effects produced by the naturally-occuring
22100	subject-process being modelled.     An interactive  simulation  model
22200	which  attempts  to  reproduce  sequences  of experienceable reality,
22300	offers an interviewer a first-hand experience with a  concrete  case.
22400	In  constructing  a  computer  simulation,  a  theory  is modelled to
22500	discover a sufficiently rich structure of hypotheses and  assumptions
22600	to  generate  the  observable  subject-behavior  under  study.      A
22700	dialogue algorithm allows an observer to  interact  with  a  concrete
22800	specimen of a class in detail. In the case of our model, the level of
22900	detail is the  level  of  the  symbolic  behavior  of  conversational
23000	language.    This  level  is  satisfying  to a clinician since he can
23100	compare the model's behavior  with  its  natural  human  counterparts
23200	using  familiar  skills  of clinical dialogue. Communicating with the
23300	paranoid model by means of  teletype,  an  interviewer  can  directly
23400	experience  for  himself  a  sample  of  the  type of impaired social
23500	relationship which develops with someone in a paranoid mode.
23600		An algorithm composed of  symbolic  computational  procedures
23700	converts  input  symbolic  structures into output symbolic structures
23800	according to certain principles.    The  modus  operandi  of  such  a
23900	symbolic  model  is simply the workings of an algorithm when run on a
24000	computer. At this level of explanation, to answer  a  "why"  question
24100	means  to  provide  an  algorithm  which  makes explicit how symbolic
24200	structures collaborate, interplay and interlock - in short, how  they
24300	are organized to generate patterns of manifest phenomena.
24400	
24500		To  simulate the sequential input-output behavior of a system
24600	using symbolic computational  procedures,  one  writes  an  algorithm
24700	which,  when run on a computer, produces symbolic behavior resembling
24800	that of the  subject  system  being  simulated.     (Colby,1973)  The
24900	resemblance  is  achieved  through  the workings of the algorithm, an
25000	organization   of   symbol-manipulating    procedures    which    are
25100	ethogenically  responsible for the characteristic observable behavior
25200	at the input-output level. Since we do not know the structure of  the
25300	"real"  simulative  processes  used  by  the  mind-brain, our posited
25400	structure stands as an imagined theoretical analogue, a possible  and
25500	plausible   organization   of  processes  analogous  to  the  unknown
25600	processes and serving as an attempt to explain their  workings.     A
25700	simulation  model  is  thus  deeper  than  a  structureless black-box
25800	explanation because it postulates functionally  equivalent  processes
25900	inside  the  box  to  account  for  outwardly  observable patterns of
26000	behavior.     A  simulation   model   constitutes   an   interpretive
26100	explanation  in  that  it  makes intelligible the connections between
26200	external input, internal states and output  by  positing  intervening
26300	symbol-processing  procedures  operating  between  symbolic input and
26400	symbolic output. To be  illuminating,  a  description  of  the  model
26500	should  make  clear  why  and  how it reacts as it does under various
26600	circumstances.
26700		Citing  a universal generalization to explain an individual's
26800	behavior is unsatisfactory to a questioner who is interested in  what
26900	powers  and liabilities are latent behind manifest phenomena.  To say
27000	"x is nasty because x is paranoid and all paranoids are nasty" may be
27100	relevant,  intelligible  and correct. But another type of explanation
27200	is possible:  a model-explanation referring to a structure which  can
27300	account  for  "nasty" behavior as a consequence of input and internal
27400	states of a system.      A  model  explanation  specifies  particular
27500	antecedents  and  processes  through  which  antecedents generate the
27600	phenomena.   An ethogenic approach to explanation assumes perceptible
27700	phenomena  display the regularities and nonrandom irregularities they
27800	do because  of  the  nature  of  an  imperceptible  and  inaccessible
27900	underlying  structure.     The  posited  theoretical  structure is an
28000	idealized analogue to the unobservable structure in persons.
28100		In  attempting  to  explain  human  behavior,  principles are
28200	involved in addition to those accounting for natural  order.  "Nature
28300	entertains  no opinions about us", said Nietzsche.  But human natures
28400	do, and therein lies a source of complexity for the	understanding
28500	of  human  conduct.  Until  the  first  quarter  of the 20th century,
28600	natural sciences were  guided  by  the  Newtonian  ideal  of  perfect
28700	process  knowledge  about  inanimate  objects whose behavior could be
28800	subsumed under lawlike generalizations.  When a deviation from a  law
28900	was noticed, it was the law which was subsequently modified, since by
29000	definition physical objects did not have the  power  to  break  laws.
29100	When  the  planet  Mercury  was  observed  to  deviate from the orbit
29200	predicted by Newtonian theory, no one accused the planet of being  an
29300	intentional  agent  disobeying  a  law. Instead it was suspected that
29400	something was incorrect about the theory.
29500		This approach using subsumptive explanation is the acceptable
29600	norm  in  many  fields.   It is seldom satisfactory in accounting for
29700	particular sequences of behavior in living purposive systems.    When
29800	physical   bodies   fall  in  the  macroscopic  world,  few  find  it
29900	scientifically useful to posit that bodies have an intention to fall.
30000	But   in   our   imagery   of   living  systems,  especially  in  our
30100	Menschanschauung, the ideal explanatory  practice  is  teleonomically
30200	Aristotelian,  utilizing  a  concept  of  intention.  (For a thorough
30300	discussion of purpose and intentionality see Boden,1972).
30400		Consider a man participating in a high-diving  contest.    In
30500	falling  towards  the water he accelerates at the rate of 32 feet per
30600	second. Viewing the man simply as a falling body, we explain his rate
30700	of  fall  by appealing to a physical law.  Viewing the man as a human
30800	intentionalistic agent, we explain his  dive  as  the  result  of  an
30900	intention  to  dive  in  a  certain  way  in  order to win the diving
31000	contest.  His conduct (in contrast  to  mere  movement)  involves  an
31100	intended  following  of certain conventional rules for what is judged
31200	by humans to constitute, say, a swan dive. Suppose part-way  down  he
31300	chooses  to  change  his  position  in  mid-air  and  enter the water
31400	thumbing his nose at the judges. He cannot disobey the law of falling
31500	bodies  but he can disobey or ignore the rules of diving. He can also
31600	make a gesture which expresses disrespect and which he believes  will
31700	be  interpreted  as  such by the onlookers.   Our diver breaks a rule
31800	for diving but follows another rule which prescribes gestural  action
31900	for  insulting  behavior.     To  explain  the  actions of diving and
32000	nose-thumbing, therefore, we would appeal, not  to  laws  of  natural
32100	order,  but  to  an  additional  order, to principles of human order.
32200	This order is superimposed on laws of natural order  and  takes  into
32300	account  (1)standards of appropriate action in certain situations and
32400	(2) the agent's inner considerations of intention, belief  and  value
32500	which  he  finds  compelling  from his point of view. In this type of
32600	explanation the explanandum, that which is being  explained,  is  the
32700	agent's  informed  actions,  not  simply his movements.  When a human
32800	agent performs an action in a situation, we can ask:  is  the  action
32900	appropriate  to  that situation and if not, why did the agent believe
33000	his action to be called for?
33100		Symbol-processing  explanations  of  human  conduct  rely  on
33200	concepts of intention, belief, action, affect,  etc.   Characteristic
33300	of  early  stages  of  explanation,  the terms for these concepts are
33400	close to the terms of ordinary language. It is also important to note
33500	that   such  terms  are  commonly  utilized  in  describing  computer
33600	algorithms which follow rules  in  striving  to  achieve  goals.  The
33700	advantage  is  that in an algorithm these ordinary language terms can
33800	be explicitly defined and represented.
33900		Psychiatry deals with the practical concerns of inappropriate
34000	action, belief, etc. on the part of a patient. The patient's behavior
34100	may  be  inappropriate  to onlookers since it represents a lapse from
34200	the expected, a contravention of the human order. It may even  appear
34300	this  way  to  the  patient  in  monitoring  and  directing  himself.
34400	Sometimes, however, the patient's behavior does not appear  anomalous
34500	to  himself.   He  maintains that anyone who understands his point of
34600	view, who conceptualizes situations as he does from the inside, would
34700	consider his outward behavior appropriate and justified. What he does
34800	not understand or accept  is  that  his  inner  conceptualization  is
34900	mistaken  and  represents  a  misinterpretation  of the events of his
35000	experience.
35100		The  model  to  be  presented  in  the  sequel constitutes an
35200	attempt to explain some regularities and  particular  occurrences  of
35300	symbolic   (conversational)   paranoid  behavior  observable  in  the
35400	clinical situation of a psychiatric interview.   The  explanation  is
35500	at the symbol-processing level of linguistically communicating agents
35600	and  is  cast  in  the  form  of  a  dialogue  algorithm.   Like  all
35700	explanations,  it  is  tentative,  incomplete,  and does not claim to
35800	represent the only conceivable structure of processes .
35900	
36000	The Nature of Algorithms
36100	
36200		Theories  can  be  presented  in various forms: prose essays,
36300	mathematical  equations  and  computer  programs.     To  date,  most
36400	theoretical  explanations in psychiatry and psychology have consisted
36500	of natural language essays with all their  well-known  vagueness  and
36600	ambiguities.   Many of these formulations have been  untestable,  not
36700	because  relevant  observations  were  lacking,  but  because  it was
36800	unclear what the  essay  was  really  saying.    Clarity  is  needed.
36900	Science  may  begin  with metaphors, but it should try to end up with
37000	algorithms.
37100		Another  way  of  formulating  psychological  theories is now
37200	available in  the  form  of  symbol-processing  algorithms,  computer
37300	programs,   which   have  the  virtue  of  being  explicit  in  their
37400	articulation and which can be run on  a  computer  to  test  internal
37500	consistency and external correspondence with the data of observation.
37600	The subject-matter (or subject) of a model is what it is a model  of;
37700	the  source of a model is what it is based upon. Since we do not know
37800	the "real" algorithms used by  people,  we  construct  a  theoretical
37900	model,  based  upon  computer algorithms.     This model represents a
38000	partial analogy. (Harre, 1970).   The partial analogy is made at  the
38100	symbol-processing  level,  not  at  the  hardware  level.           A
38200	functional,  computational  or  procedural   equivalence   is   being
38300	postulated.      The  question  then  becomes one of categorizing the
38400	extent of the equivalence.         A beginning  (first-approximation)
38500	functional  equivalence  might  be defined as indistinguishability at
38600	the level of observable I-O  pairs.   A  stronger  equivalence  would
38700	consist  of indistinguishability at inner I-O levels.  That is, there
38800	exists a correspondence between what is being  done  and  how  it  is
38900	being done at a given operational level.
39000		An  algorithm represents an organization of symbol-processing
39100	strategies or functions which represent an "effective procedure".  An
39200	effective procedure consists of three components:
39300	
39400		(1) A programming language in which procedural rules of
39500		    behavior can be rigorously and unambiguously specified.
39600		(2) An organization of procedural rules which constitute 
39700		    the algorithm.
39800		(3) A machine processor which can rapidly and reliably carry
39900		    out the processes specified by the procedural rules.
40000	The  specifications  of  (2),  written  in   the   formally   defined
40100	programming  language  of  (1),  are  termed  an algorithm or program
40200	whereas (3) involves a computer as the machine processor - a  set  of
40300	deterministic  physical  mechanisms  which can perform the operations
40400	specified in the algorithm.   The  algorithm  is  called  "effective"
40500	because  it  actually works, performing as intended and producing the
40600	effects desired by  the  model  builders  when  run  on  the  machine
40700	processor.
40800		A simulation model is composed  of  procedures  taken  to  be
40900	analogous   to  imperceptible  and  inaccessible  procedures  of  the
41000	mind-brain.  We are not claiming they ARE analogous,  we  are  MAKING
41100	them so.  The analogy being drawn here is between specified processes
41200	and their generating systems.  Thus, in comparing mental processes to
41300	computational processes, we might assert:
41400	
41500	      mental process    computational process
41600	      --------------:: ----------------------
41700	      brain hardware      computer hardware and
41800	      and programs           programs
41900	
42000		Many of the classical mind-brain problems arose because there
42100	did not exist a familiar,  well-understood  analogy  to  help  people
42200	imagine how a system could work having a clear separation between its
42300	hardware descriptions and its program descriptions.  With the  advent
42400	of  computers  and  programs  some mind-brain perplexities disappear.
42500	(Colby,1971).  The analogy is not simply  between  computer  hardware
42600	and  brain  wetware.   We  are not comparing the structure of neurons
42700	with the structure of transistors; we are comparing the
42800	organization of symbol-processing procedures  in  an  algorithm  with
42900	symbol-processing  procedures of the mind-brain.  The central nervous
43000	system contains a representation of the experience of its holder.   A
43100	model  builder has a conceptual representation of that representation
43200	which he demonstrates in the form of a model.  Thus the  model  is  a
43300	demonstration of a representation of a representation.
43400		An  algorithm  can  be  run  on  a  computer  in two forms, a
43500	compiled version and an interpreted version. In the compiled  version
43600	a  preliminary  translation  has  been  made  from  the  higher-level
43700	programming  language  (source  language)  into  lower-level  machine
43800	language  (object  language)  which  controls  the  on-off  state  of
43900	hardware switching devices. When the compiled  version  is  run,  the
44000	instructions  of  the machine-language code are directly executed. In
44100	the interpreted version each high-level language instruction is first
44200	translated  into  machine language, executed, and then the process is
44300	repeated with the next instruction.   One  important  aspect  of  the
44400	distinction  between  compiled  and  interpreted versions is that the
44500	compiled version, now written in  machine  language,  is  not  easily
44600	accessible  to  change  using  the higher-level language. In order to
44700	change the program, the interpreted version must be modified  in  the
44800	source  language  and then re-compiled into the object language.  The
44900	rough analogy with ever-changing  human  symbolic  behavior  lies  in
45000	suggesting  that  modifications require change at the source-language
45100	level. Otherwise compiled algorithms are inaccessible to second order
45200	monitoring and modification.
45300		Since we are taking running computer programs as a source  of
45400	analogy for a paranoid model, logical errors or pathological behavior
45500	on  the  part   of   such   programs   are   of   interest   to   the
45600	psychopathologist.   These  errors  can  be  ascribed to the hardware
45700	level, to the interpreter, or to the programs  which  the  interpreter
45800	executes.    Different  remedies are required at different levels. If
45900	the analogy  is  to  be  clinically  useful  in  the  case  of  human
46000	pathological  behavior,  it  will  become  a  matter  of  influencing
46100	symbolic behavior with the appropriate techniques.
46200		Since  the algorithm is written in a programming language, it
46300	is hermetic except to a few people,  who  in  general  do  not  enjoy
46400	reading   other  people's  code.     Hence  the  intelligibility  and
46500	scrutability requirement for explanations must be met in other  ways.
46600	In  an attempt to open the algorithm to scrutiny I shall describe the
46700	model in detail using diagrams and interview examples profusely.
46800	
46900	
47000	Analogy
47100	
47200		I  have  stated  that  an  interactive  simulation  model  of
47300	symbol-manipulating  processes  reproduces  sequences   of   symbolic
47400	behavior  at the level of linguistic communication.  The reproduction
47500	is achieved through the operations of an algorithm consisting  of  an
47600	organization   of   hypothetical   symbol-processing   strategies  or
47700	procedures which can  generate  the  I-O  behavior  of  the  subject-
47800	processes   under  investigation. The   algorithm  is  an  "effective
47900	procedure" in the sense it really works in the manner intended by the
48000	model-builders.  In the model to be described, the paranoid algorithm
48100	generates  linguistic  I-O  behavior  typical   of   patients   whose
48200	symbol-processing  is dominated by the paranoid mode. Comparisons can
48300	be made between samples of the I-O behaviors of patients  and  model.
48400	But  the  analogy is not to be drawn at this level.   Mynah birds and
48500	tape recorders also reproduce human linguistic behavior, but  no  one
48600	believes  the  reproduction  is achieved by powers analogous to human
48700	powers.   Given that the manifest outermost I-O behavior of the model
48800	is  indistinguishable  from  the  manifest  outward  I-O  behavior of
48900	paranoid patients, does this imply that the  hypothetical  underlying
49000	processes  used  by  the  model are analogous to (or perhaps the same
49100	as?) the underlying processes used by persons in the  paranoid  mode?
49200	This deep and far-reaching question should be approached with caution
49300	and only when we are  first  armed  with  some  clear  notions  about
49400	analogy, similarity, faithful reproduction, indistinguishability  and
49500	functional equivalence.
49600		In comparing two things (objects, systems or processes )  one
49700	can   cite   properties  they  have  in  common  (positive  analogy),
49800	properties they do not share (negative analogy) and properties as  to
49900	which  we  do not know whether they are positive or negative (neutral
50000	analogy). (See Hesse,1966). No two things are exactly alike in  every
50100	detail.    If  they were identical in respect to all their properties
50200	then they would be copies. If they were identical  in  every  respect
50300	including  their  spatio-temporal  location we would say we have only
50400	one thing instead of two. Everything  resembles  something  else  and
50500	maybe everything else, depending upon how one cites properties.
50600		In an analogy a similarity relation is  evoked.  "Newton  did
50700	not  show  the  cause of the apple falling but he showed a similitude
50800	between the apple and the stars."(D`Arcy Thompson). Huygens suggested
50900	an analogy between sound waves and light waves in order to understand
51000	something less well-understood (light) in terms of  something  better
51100	understood   (sound).   To  account  for  species  variation,  Darwin
51200	postulated a  process  of  natural  selection.    He  constructed  an
51300	analogy  from two sources, one from artificial selection as practiced
51400	by domestic breeders of animals and one from  Malthus'  theory  of  a
51500	competition  for  existence  in a population increasing geometrically
51600	while its resources increase arithmetically. Bohr's model of the atom
51700	offered  an  analogy  between solar system and atom. These well-known
51800	historical examples should be sufficient here to illustrate the  role
51900	of analogies in theory construction.    Analogies are made in respect
52000	to  those  properties  which  constitute  the  positive  and  neutral
52100	analogy.     The  negative analogy is ignored.   Thus Bohr's model of
52200	the atom as a miniature planetary system was not intended to  suggest
52300	that  electrons  possessed  color or that planets jumped out of their
52400	orbits. 
52500	
52600	Functional Equivalence
52700	
52800		When human symbolic processes are the subject of a simulation
52900	model, we draw the analogy from two sources, symbolic computation and
53000	psychology.  The analogy made is between systems known  to  have  the
53100	power  to  process  symbols, namely, persons and computers.       The
53200	properties compared in the analogy  are  obviously  not  physical  or
53300	morphological such as blood and wires, but functional and procedural.
53400	We want to assume that not-well-understood  mental  procedures  in  a
53500	person  are  similar  to  the  more  accessible and better understood
53600	procedures of symbol-processing which take place in a computer.   The
53700	analogy  is  one  of  functional  or  procedural equivalence.  (For a
53800	further account of functional analysis see Hempel, 1965).  Mousetraps
53900	are  functionally equivalent.    There exists a large set of physical
54000	mechanisms for catching mice. The term  "mousetrap"  says  what  each
54100	member  of  the  set has in common.  Each takes as input a live mouse
54200	and yields as output a dead one. Systems equivalent from one point of
54300	view may not be equivalent from another (Fodor,1968).
54400		If  model  and  human  are  indistinguishable at the manifest
54500	level of linguistic I-O pairs, then they can be considered equivalent
54600	at  that  level.      If they can be shown to be indistinguishable at
54700	more internal symbolic levels, then a  stronger  equivalence  exists.
54800	How  stringent  and  how extensive are the demands for equivalence to
54900	be? Must the correspondence be point-to-point or can it be  the  more
55000	global system-to-system? Must there be point-to-point correspondences
55100	at every level? What is to count as a point and what are the  levels?
55200	Procedures  can  be  specified  and  ostensively  pointed  to  in  an
55300	algorithm, but how can we point to unobservable symbolic processes in
55400	a  person?    There  is  an  inevitable  limit  to  scrutinizing  the
55500	"underlying"  processes  of  the  world.     Einstein  likened   this
55600	situation to a man explaining the behavior of a watch without opening
55700	it: "He will never be able to  compare  his  picture  with  the  real
55800	mechanism  and  he  cannot even imagine the possibility or meaning of
55900	such a comparison".
56000		In  constructing  an   algorithm   one   puts   together   an
56100	organization  of  collaborating  functions or procedures.  A function
56200	takes some symbolic structure  as  input  and  yields  some  symbolic
56300	structure as output. Two computationally equivalent functions, having
56400	the same input and yielding the same output, can differ "inside"  the
56500	function at the instruction level.
56600		Consider  an elementary programming problem which students in
56700	symbolic computation are often asked to solve.  Given  a  list  L  of
56800	symbols,  L=(A  B  C  D), as input, construct a function or procedure
56900	which will convert this list to the list RL in which the order of the
57000	symbols  is  reversed,  i.e.   RL=(D  C B A).  There are many ways of
57100	solving this problem and the code of one student may  differ  greatly
57200	from that of another at the level of individual instructions. But the
57300	differences of such details are irrelevant. What  is  significant  is
57400	that  the  solutions  make  the required conversion from L to RL. The
57500	correct solutions will  all  be  computationally  equivalent  at  the
57600	input-output  level  since  they take the same symbolic structures as
57700	input and produce the same symbolic output.
57800		If  we  propose  that  an  algorithm  we  have constructed is
57900	functionally equivalent to what goes on in humans when  they  process
58000	symbolic   structures,   how   can   we   justify   this  position  ?
58100	Indistinguishability tests at,  say,  the  linguistic  level  provide
58200	evidence  only for beginning equivalence. We would like to be able to
58300	have access to the underlying processes in humans the way we can with
58400	algorithms.  (Admittedly, we do not directly observe processes at all
58500	levels but only  the  products  of  some).  The  difficulty  lies  in
58600	identifying,  making  accessible,  and  counting  processes  in human
58700	heads.    Many symbol-processing experiments are now  being  designed
58800	and  carried  out.  We  must  have  great  patience with this type of
58900	experimental information-processing psychology.
59000		In  the meantime, besides first-approximation I-O equivalence
59100	and plausibility arguments,  one  might  appeal  to  extra-evidential
59200	support  offering  parallelisms  from neighboring scientific domains.
59300	One can offer analogies between what is known to go on at a molecular
59400	level  in  the  cells  of  living  organisms  and  what goes on in an
59500	algorithm. For example, a DNA molecule  in  the  nucleus  of  a  cell
59600	consists  of an ordered sequence (list) of nucleotide bases (symbols)
59700	coded in triplets termed codons (words). Each element  of  the  codon
59800	specifies  which  amino acid during protein synthesis is to be linked
59900	into the chain of polypeptides making up the  protein.    The  codons
60000	function like instructions in a programming language. Some codons are
60100	known to operate as terminal  symbols  analogous  to  symbols  in  an
60200	algorithm  which  terminate  the  end of a list. If, as a result of a
60300	mutation, a nucleotide base is changed, the usual protein will not be
60400	synthesized.  The  polypeptide  chain  resulting  may  have lethal or
60500	trivial consequences for the  organism  depending  on  what  must  be
60600	passed  on to other processes which require polypeptides to be handed
60700	over to them. Similarly in an algorithm. If a symbol  or  word  in  a
60800	procedure  is incorrect, the procedure cannot operate in its intended
60900	manner.   Such a result may be lethal or  trivial  to  the  algorithm
61000	depending  on  what  information the faulty procedure must pass on at
61100	its interface with other procedures in the overall organization. Each
61200	procedure   in  an  algorithm  is  embedded  in  an  organization  of
61300	collaborating procedures just as are functions in  living  organisms.
61400	We  know that at the molecular level of living organisms there exists
61500	a process such as serial progression  along  a  nucleotide  sequence,
61600	which is analogous to stepping down a list in an algorithm.   Further
61700	analogies can be made between point mutations in which DNA bases  can
61800	be   inserted,   deleted,   substituted  or  reordered  and  symbolic
61900	computation in which the same operations are commonly carried out  on
62000	symbolic    structures.     Such   analogies   are   interesting   as
62100	extra-evidential support but obviously  closer  linkages  are  needed
62200	between  the macro-level of symbolic processes and the micro-level of
62300	molecular information-processing within cells.
62400		To obtain evidence  for  the  acceptability  of  a  model  as
62500	faithful  or  authentic,  empirical  tests are utilized as validation
62600	procedures. Such tests should also tell us which is  the  best  among
62700	alternative  versions  of  a  family  of  models  and,  indeed  among
62800	alternative families of models.  Scientific explanations do not stand
62900	alone  in  isolation. They are evaluated relative to rival contenders
63000	for the position of "best available".  Once we  accept  a  theory  or
63100	model as the best available, can we be sure it is correct or true? We
63200	can never know with certainty. Theories and  models  are  provisional
63300	and  partial  approximations  to  nature  destined  in time to become
63400	abandoned and superseded by better ones.