CIRCULAR REASONING INVOLVES ASSUMING AS A PREMISE THAT WHICH YOU ARE TRYING
TO PROVE. INTUITIVELY, IT MAY SEEM THAT NO ONE WOULD FALL FOR SUCH AN ARGUME
NT. HOWEVER, THE CONCLUSION MAY APPEAR TO STATE SOMETHING ADDITIONAL, OR THE
ARGUMENT MAY BE SO LONG THAT THE READER MAY FORGET THAT THE CONCLUSION WAS
STATED AS A PREMISE.
EXAMPLE:
THE DEATH PENALTY IS APPROPRIATE FOR TRAITORS BECAUSE IT IS RIGHT TO EXECUTE
THOSE WHO BETRAY THEIR OWN COUNTRY AND THEREBY RISK THE LIVES OF MILLIONS.
THIS ARGUMENT IS CIRCULAR BECAUSE "RIGHT" MEANS ESSENTIALLY THE SAME THING A
S "APPROPRIATE." IN EFFECT, THE WRITER IS SAYING THAT THE DEATH PENALTY IS A
PPROPRIATE BECAUSE IT IS APPROPRIATE.
SHIFTING THE BURDEN OF PROOF
IT IS INCUMBENT ON THE WRITER TO PROVIDE EVIDENCE OR SUPPORT FOR HER POSITIO
N. TO IMPLY THAT A POSITION IS TRUE MERELY BECAUSE NO ONE HAS DISPROVED IT I
S TO SHIFT THE BURDEN OF PROOF TO OTHERS.
EXAMPLE:
SINCE NO ONE HAS BEEN ABLE TO PROVE GOD’S EXISTENCE, THERE MUST NOT BE A GOD
..
THERE ARE TWO MAJOR WEAKNESSES IN THIS ARGUMENT. FIRST, THE FACT THAT GOD’S
EXISTENCE HAS YET TO BE PROVEN DOES NOT PRECLUDE ANY FUTURE PROOF OF EXISTEN
CE. SECOND, IF THERE IS A GOD, ONE WOULD EXPECT THAT HIS EXISTENCE IS INDEPE
NDENT OF ANY PROOF BY MAN.
UNWARRANTED ASSUMPTIONS
THE FALLACY OF UNWARRANTED ASSUMPTION IS COMMITTED WHEN THE CONCLUSION OF AN
ARGUMENT IS BASED ON A PREMISE (IMPLICIT OR EXPLICIT) THAT IS FALSE OR UNWA
RRANTED. AN ASSUMPTION IS UNWARRANTED WHEN IT IS FALSE--THESE PREMISES ARE U
SUALLY SUPPRESSED OR VAGUELY WRITTEN. AN ASSUMPTION IS ALSO UNWARRANTED WHEN
IT IS TRUE BUT DOES NOT APPLY IN THE GIVEN CONTEXT--THESE PREMISES ARE USUA
LLY EXPLICIT.
EXAMPLE: (FALSE DICHOTOMY)
EITHER RESTRICTIONS MUST BE PLACED ON FREEDOM OF SPEECH OR CERTAIN SUBVERSIV
E ELEMENTS IN SOCIETY WILL USE IT TO DESTROY THIS COUNTRY. SINCE TO ALLOW TH
E LATTER TO OCCUR IS UNCONSCIONABLE, WE MUST RESTRICT FREEDOM OF SPEECH.
THE CONCLUSION ABOVE IS UNSOUND BECAUSE
(A) SUBVERSIVES DO NOT IN FACT WANT TO DESTROY THE COUNTRY
(B) THE AUTHOR PLACES TOO MUCH IMPORTANCE ON THE FREEDOM OF SPEECH
(C) THE AUTHOR FAILS TO CONSIDER AN ACCOMMODATION BETWEEN THE TWO ALTERNATIV
ES
(D) THE MEANING OF "FREEDOM OF SPEECH" HAS NOT BEEN DEFINED
(E) SUBVERSIVES ARE A TRUE THREAT TO OUR WAY OF LIFE
THE ARGUER OFFERS TWO OPTIONS: EITHER RESTRICT FREEDOM OF SPEECH, OR LOSE TH
E COUNTRY. HE HOPES THE READER WILL ASSUME THAT THESE ARE THE ONLY OPTIONS A
VAILABLE. THIS IS UNWARRANTED. HE DOES NOT STATE HOW THE SO-CALLED "SUBVERSI
VE ELEMENTS" WOULD DESTROY THE COUNTRY, NOR FOR THAT MATTER, WHY THEY WOULD
WANT TO DESTROY IT. THERE MAY BE A THIRD OPTION THAT THE AUTHOR DID NOT MENT
ION; NAMELY, THAT SOCIETY MAY BE ABLE TO TOLERATE THE "SUBVERSIVES" AND IT M
AY EVEN BE IMPROVED BY THE DIVERSITY OF OPINION THEY OFFER. THE ANSWER IS (C
).
APPEAL TO AUTHORITY
TO APPEAL TO AUTHORITY IS TO CITE AN EXPERT’S OPINION AS SUPPORT FOR ONE’S O
WN OPINION. THIS METHOD OF THOUGHT IS NOT NECESSARILY FALLACIOUS. CLEARLY, T
HE REASONABLENESS OF THE ARGUMENT DEPENDS ON THE "EXPERTISE" OF THE PERSON B
EING CITED AND WHETHER SHE IS AN EXPERT IN A FIELD RELEVANT TO THE ARGUMENT.
APPEALING TO A DOCTOR’S AUTHORITY ON A MEDICAL ISSUE, FOR EXAMPLE, WOULD BE
REASONABLE; BUT IF THE ISSUE IS ABOUT DERMATOLOGY AND THE DOCTOR IS AN ORTH
OPEDIST, THEN THE ARGUMENT WOULD BE QUESTIONABLE.
PERSONAL ATTACK
IN A PERSONAL ATTACK (AD HOMINEM), A PERSON’S CHARACTER IS CHALLENGED INSTEA
D OF HER OPINIONS.
EXAMPLE:
POLITICIAN: HOW CAN WE TRUST MY OPPONENT TO BE TRUE TO THE VOTERS? HE ISN’T
TRUE TO HIS WIFE!
THIS ARGUMENT IS WEAK BECAUSE IT ATTACKS THE OPPONENT’S CHARACTER, NOT HIS P
OSITIONS. SOME PEOPLE MAY CONSIDER FIDELITY A PREREQUISITE FOR PUBLIC OFFICE
.. HISTORY, HOWEVER, SHOWS NO CORRELATION BETWEEN FIDELITY AND GREAT POLITICA
L LEADERSHIP.
--
I WOULD FLY YOU TO THE MOON AND BACK
IF YOU’LL BE IF YOU’LL BE MY BABY
GOT A TICKET FOR A WORLDSWHERESWE BELONG
SO WOULD YOU BE MY BABY
TESTPREP充分性精解转载SMTH 2001-10-14 10:51:58发信人: YKK (我不说话并不代表我不在乎),信区: ENGLISHTEST
标题: (GMAT)TESTPREP充分性精解
发信站: BBS水木清华站(FRI OCT 12 16:07:05 2001)
DATA SUFFICIENCY
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INTRODUCTION DATA SUFFICIENCY
MOST PEOPLE HAVE MUCH MORE DIFFICULTY WITH THE DATA SUFFICIENCY PROBLEMS THA
N WITH THE STANDARD MATH PROBLEMS. HOWEVER, THE MATHEMATICAL KNOWLEDGE AND S
KILL REQUIRED TO SOLVE DATA SUFFICIENCY PROBLEMS IS NO GREATER THAN THAT REQ
UIRED TO SOLVE STANDARD MATH PROBLEMS. WHAT MAKES DATA SUFFICIENCY PROBLEMS
APPEAR HARDER AT FIRST IS THE COMPLICATED DIRECTIONS. BUT ONCE YOU BECOME FA
MILIAR WITH THE DIRECTIONS, YOU’LL FIND THESE PROBLEMS NO HARDER THAN STANDA
RD MATH PROBLEMS. IN FACT, PEOPLE USUALLY BECOME PROFICIENT MORE QUICKLY ON
DATA SUFFICIENCY PROBLEMS.
THE DIRECTIONS
THE DIRECTIONS FOR DATA SUFFICIENCY QUESTIONS ARE RATHER COMPLICATED. BEFORE
READING ANY FURTHER, TAKE SOME TIME TO LEARN THE DIRECTIONS COLD. SOME OF T
HE WORDING IN THE DIRECTIONS BELOW HAS BEEN CHANGED FROM THE GMAT TO MAKE IT
CLEARER. YOU SHOULD NEVER HAVE TO LOOK AT THE INSTRUCTIONS DURING THE TEST.
DIRECTIONS: EACH OF THE FOLLOWING DATA SUFFICIENCY PROBLEMS CONTAINS A QUEST
ION FOLLOWED BY TWO STATEMENTS, NUMBERED (1) AND (2). YOU NEED NOT SOLVE THE
PROBLEM; RATHER YOU MUST DECIDE WHETHER THE INFORMATION GIVEN IS SUFFICIENT
TO SOLVE THE PROBLEM.
THE CORRECT ANSWER TO A QUESTION IS
A IF STATEMENT (1) ALONE IS SUFFICIENT TO ANSWER THE QUESTION BUT STATEMENT
(2) ALONE IS NOT SUFFICIENT;
B IF STATEMENT (2) ALONE IS SUFFICIENT TO ANSWER THE QUESTION BUT STATEMENT
(1) ALONE IS NOT SUFFICIENT;
C IF THE TWO STATEMENTS TAKEN TOGETHER ARE SUFFICIENT TO ANSWER THE QUESTION
, BUT NEITHER STATEMENT ALONE IS SUFFICIENT;
D IF EACH STATEMENT ALONE IS SUFFICIENT TO ANSWER THE QUESTION;
E IF THE TWO STATEMENTS TAKEN TOGETHER ARE STILL NOT SUFFICIENT TO ANSWER TH
E QUESTION.
NUMBERS: ONLY REAL NUMBERS ARE USED. THAT IS, THERE ARE NO COMPLEX NUMBERS.
DRAWINGS: THE DRAWINGS ARE DRAWN TO SCALE ACCORDING TO THE INFORMATION GIVEN
IN THE QUESTION, BUT MAY CONFLICT WITH THE INFORMATION GIVEN IN STATEMENTS
(1) AND (2).
YOU CAN ASSUME THAT A LINE THAT APPEARS STRAIGHT IS STRAIGHT AND THAT ANGLE
MEASURES CANNOT BE ZERO.
YOU CAN ASSUME THAT THE RELATIVE POSITIONS OF POINTS, ANGLES, AND OBJECTS AR
E AS SHOWN.
ALL DRAWINGS LIE IN A PLANE UNLESS STATED OTHERWISE.
EXAMPLE:
IN TRIANGLE ABC TO THE RIGHT, WHAT IS THE VALUE OF Y?
(1) AB = AC
(2) X = 30
EXPLANATION: BY STATEMENT (1), TRIANGLE ABC IS ISOSCELES. HENCE, ITS BASE AN
GLES ARE EQUAL: Y = Z. SINCE THE ANGLE SUM OF A TRIANGLE IS 180 DEGREES, WE
GET X + Y + Z = 180. REPLACING Z WITH Y IN THIS EQUATION AND THEN SIMPLIFYIN
G YIELDS X + 2Y = 180. SINCE STATEMENT (1) DOES NOT GIVE A VALUE FOR X, WE C
ANNOT DETERMINE THE VALUE OF Y FROM STATEMENT (1) ALONE. BY STATEMENT (2), X
= 30. HENCE, X + Y + Z = 180 BECOMES 30 + Y + Z = 180, OR Y + Z = 150. SINC
E STATEMENT (2) DOES NOT GIVE A VALUE FOR Z, WE CANNOT DETERMINE THE VALUE O
F Y FROM STATEMENT (2) ALONE. HOWEVER, USING BOTH STATEMENTS IN COMBINATION,
WE CAN FIND BOTH X AND Z AND THEREFORE Y. HENCE, THE ANSWER IS C.
NOTICE IN THE ABOVE EXAMPLE THAT THE TRIANGLE APPEARS TO BE A RIGHT TRIANGLE
.. HOWEVER, THAT CANNOT BE ASSUMED: ANGLE A MAY BE 89 DEGREES OR 91 DEGREES,
WE CAN’T TELL FROM THE DRAWING. YOU MUST BE VERY CAREFUL NOT TO ASSUME ANY M
ORE THAN WHAT IS EXPLICITLY GIVEN IN A DATA SUFFICIENCY PROBLEM.
ELIMINATION
DATA SUFFICIENCY QUESTIONS PROVIDE FERTILE GROUND FOR ELIMINATION. IN FACT,
IT IS RARE THAT YOU WON’T BE ABLE TO ELIMINATE SOME ANSWER-CHOICES. REMEMBER
, IF YOU CAN ELIMINATE AT LEAST ONE ANSWER CHOICE, THE ODDS OF GAINING POINT
S BY GUESSING ARE IN YOUR FAVOR.
THE FOLLOWING TABLE SUMMARIZES HOW ELIMINATION FUNCTIONS WITH DATA SUFFICIEN
CY PROBLEMS.
STATEMENT CHOICES ELIMINATED
(1) IS SUFFICIENT B, C, E
(1) IS NOT SUFFICIENT A, D
(2) IS SUFFICIENT A, C, E
(2) IS NOT SUFFICIENT B, D
(1) IS NOT SUFFICIENT AND (2) IS NOT SUFFICIENT A, B, D
EXAMPLE 1: WHAT IS THE 1ST TERM IN SEQUENCE S?
(1) THE 3RD TERM OF S IS 4.
(2) THE 2ND TERM OF S IS THREE TIMES THE 1ST, AND THE 3RD TERM IS FOUR TIMES
THE 2ND.
(1) IS NO HELP IN FINDING THE FIRST TERM OF S. FOR EXAMPLE, THE FOLLOWING SE
QUENCES EACH HAVE 4 AS THEIR THIRD TERM, YET THEY HAVE DIFFERENT FIRST TERMS
:
0, 2, 4
责任编辑：sealion1986
