Principles of Economics by Alfred Marshall 马歇尔的经济学原理（英文版) txt+doc+PDF+MP3
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Principles of Economics
Alfred Marshall
Principles of Economics
An Introductory Volume
Natura non facit saltum
PREFACE TO THE FIRST EDITION.


Economic conditions are constantly changing, and each generationlooks atits
own problemsinits own way.In England, as well as onthe Continent andin
America, Economicstudies are being more vigorously pursued nowthan ever
before;butallthisactivityhasonlyshownthemoreclearlythatEconomic
scienceis, and must be, one of slow and continuous growth. Some ofthe best
workofthepresentgenerationhasindeedappearedatfirstsighttobe
antagonistictothat of earlier writers; but whenit has hadtimetosettle down
intoitsproperplace,anditsroughedgeshavebeen wornaway,ithasbeen
found to involve no real breach of continuity in the development of the science.
The new doctrines have supplemented the older, have extended, developed, and
sometimes corrected them, and often have given them a different tone by a new
distribution of emphasis; but very seldom have subverted them.

P.1
The presenttreatiseis an attemptto present a modern version of old doctrines
withthe aid ofthe new work, and withreferencetothe new problems, of our
own age.Its general scope and purpose areindicatedin BookI.; atthe end of
whichashortaccountisgivenof whataretakentobethechiefsubjectsof
economicinquiry,andthechiefpracticalissueson whichthatinquiryhasa
bearing. In accordance with English traditions, it is held that the function of the
scienceistocollect,arrangeandanalyseeconomicfacts,andtoapplythe
knowledge,gainedbyobservationandexperience,indeterminingwhatare
likely to be the immediate and ultimate effects of various groups of causes; and
it is held that the Laws of Economics are statements of tendencies expressed in
the indicative mood, and not ethical precepts in the imperative. Economic laws
andreasoningsinfact are merely a part ofthe material which Conscience and
Common-sensehavetoturntoaccountinsolvingpracticalproblems,andin
laying down rules which may be a guide in life.

P.2
But ethical forces are among those of which the economist has to take account.
Attempts have indeed been made to construct an abstract science with regard to
the actions of an "economic man," who is under no ethical influences and who
pursues pecuniary gain warily and energetically, but mechanically and selfishly.
Buttheyhavenotbeensuccessful,noreventhoroughlycarriedout. Forthey
have never really treated the economic man as perfectly selfish: no one could be
reliedonbettertoenduretoilandsacrifice withtheunselfishdesireto make
provisionforhisfamily;andhisnormalmotiveshavealwaysbeentacitly
P.3 assumed to include the family affections. But if they include these, why should
they not include all other altruistic motives the action of which is so far uniform
in any class at any time and place, that it can be reduced to general rule? There
seems to be no reason; and in the present book normal action is taken to be that
whichmaybeexpected,undercertainconditions,fromthemembersofan
industrialgroup;andnoattemptismadetoexcludetheinfluenceofany
motives, the action of which is regular, merely because they are altruistic. If the
book has any special character of its own, that may perhaps be said to lie in the
prominencewhichitgivestothisandotherapplicationsofthePrincipleof
Continuity.

This principle is applied not only to the ethical quality of the motives by which
a man maybeinfluencedinchoosinghisends,butalsotothesagacity,the
energy and the enterprise with which he pursues those ends. Thus stress is laid
onthefactthatthereis a continuous gradationfromthe actions of "city men,"
whicharebasedondeliberateandfar-reachingcalculations,andareexecuted
with vigour and ability, to those of ordinary people who have neither the power
northewilltoconducttheiraffairsinabusiness-likeway.Thenormal
willingnessto save,the normal willingnessto undergo a certain exertionfor a
certainpecuniaryreward,orthenormalalertnesstoseekthebest marketsin
whichto buyandsell, ortosearch outthe most advantageous occupationfor
oneself orfor one's children—allthese and similar phrases must berelativeto
the members ofa particularclassat a given place andtime: but, whenthatis
once understood,thetheory of normal valueis applicabletothe actions ofthe
unbusiness-like classes in the same way, though not with the same precision of
detail, as to those of the merchant or banker.

P.4
And as there is no sharp line of division between conduct which is normal, and
thatwhichhastobeprovisionallyneglectedasabnormal,sothereisnone
betweennormalvaluesand"current"or"market" or"occasional"values. The
latterarethosevaluesinwhichtheaccidentsofthemomentexerta
preponderatinginfluence;whilenormalvaluesarethosewhichwouldbe
ultimately attained, if the economic conditions under view had time to work out
undisturbed their full effect. But there is no impassable gulf between these two;
theyshadeintooneanotherbycontinuousgradations.Thevalues which we
may regard as normal if we are thinking of the changes from hour to hour on a
Produce Exchange, do butindicate current variations withregardtothe year's
history:andthenormalvalueswithreferencetotheyear'shistoryarebut
current values withreferencetothe history ofthe century. Forthe element of
Time,whichisthecentreofthechiefdifficultyofalmosteveryeconomic
problem,isitself absolutely continuous: Nature knows no absolute partition of
timeintolongperiodsandshort;butthetwoshadeintooneanotherby
imperceptible gradations, and whatis a short period for one problem,is along
period for another.
Thusforinstancethegreaterpart,thoughnotthewhole,ofthedistinction
between Rent and Interest on capital turns on the length of the period which we
havein view. That whichisrightlyregarded asinterest on "free" or "floating"
capital, or on newinvestments of capital,is more properlytreated as a sort of
P.6 rent—a Quasi-rent it is called below—on old investments of capital. And there
isnosharplineofdivisionbetweenfloatingcapitalandthat whichhasbeen
"sunk" for a special branch of production, nor between new and old investments
of capital; each group shades into the other gradually. And thus even the rent of
land is seen, not as a thing by itself, but as the leading species of a large genus;
though indeed it has peculiarities of its own which are of vital importance from
the point of view of theory as well as of practice.

Again,thoughthereisasharplineofdivisionbetween manhimselfandthe
appliances which he uses; and though the supply of, and the demand for, human
efforts and sacrifices have peculiarities of their own, which do not attach to the
supplyof,andthedemandfor,materialgoods;yet,afterall,these material
goods arethemselves generallytheresult of human efforts and sacrifices. The
theoriesofthevaluesoflabour,andofthethingsmadebyit,cannotbe
separated:theyarepartsofonegreatwhole;andwhatdifferencesthereare
betweenthem evenin matters of detail,turn out oninquiryto be,forthe most
part,differencesofdegreeratherthanofkind.As,inspiteofthegreat
differencesinformbetweenbirdsandquadrupeds,thereisoneFundamental
Idea running through all their frames, so the general theory of the equilibrium of
demand and supply is a Fundamental Idea running through the frames of all the
various parts of the central problem of Distribution and Exchange*1
.

P.7
Another application of the Principle of Continuityis to the use of terms. There
hasalwaysbeenatemptationtoclassifyeconomicgoodsinclearlydefined
groups, about which a number of short and sharp propositions could be made, to
gratify at oncethe student's desireforlogical precision, andthe popularliking
for dogmasthat havethe air of being profound and are yet easily handled. But
greatmischiefseemstohavebeendonebyyieldingtothistemptation,and
drawingbroadartificiallinesofdivisionwhereNaturehasmadenone.The
moresimpleandabsoluteaneconomicdoctrineis,thegreaterwillbethe
confusion which it brings into attempts to apply economic doctrines to practice,
if the dividing lines to which it refers cannot be found in real life. There is not in
reallife a clearline of division betweenthingsthat are and are not Capital, or
thatareandarenotNecessaries,oragainbetweenlabourthatisandisnot
Productive.

P.8 The notion of continuity withregardto developmentis commonto all modern
schools ofeconomicthought, whetherthechiefinfluencesacting onthem are
thoseofbiology,asrepresentedbythewritingsofHerbertSpencer;orof
history and philosophy, as represented by Hegel's Philosophy of History, and by
more recent ethico-historical studies on the Continent and elsewhere. These two
kindsofinfluenceshaveaffected, morethananyother,thesubstanceofthe
views expressedinthe present book; buttheirform has been most affected by
mathematicalconceptionsofcontinuity,asrepresentedin Cournot's Principes
MathématiquesdelaThéoriedes Richesses. Hetaughtthatitisnecessaryto
face the difficulty of regarding the various elements of an economic problem,—
notasdeterminingoneanotherinachainofcausation,AdeterminingB,B
determiningC,andsoon—butasallmutuallydeterminingoneanother.
Nature's action is complex: and nothing is gained in the long run by pretending
that it is simple, and trying to describe it in a series of elementary propositions.

P.9
Under the guidance of Cournot, and in a less degree of von Thünen, I was led to
attach great importance to the fact that our observations of nature, in the moral
asinthephysicalworld,relatenotsomuchtoaggregatequantities,asto
incrementsofquantities,andthatinparticularthedemandforathingisa
continuousfunction,ofwhichthe"marginal
*2
"incrementis,instable
equilibrium,balancedagainstthecorrespondingincrementofitscostof
production.Itisnoteasytogetaclearfullviewofcontinuityinthisaspect
withoutthe aid either of mathematical symbols or of diagrams. The use ofthe
latterrequiresnospecial knowledge,andtheyoftenexpresstheconditions of
economiclife moreaccurately,as wellas moreeasily,thando mathematical
symbols; and therefore they have been applied as supplementary illustrations in
the footnotes of the present volume. The argument in the text is never dependent
on them; and they may be omitted; but experience seems to show that they give
afirmer grasp of manyimportant principlesthan can be got withouttheir aid;
andthatthere are many problems of puretheory, which no one who has once
learnt to use diagrams will willingly handle in any other way.

P.10
The chief use of pure mathematics in economic questions seems to be in helping
a person to write down quickly, shortly and exactly, some of his thoughts for his
own use: and to make sure that he has enough, and only enough, premisses for
his conclusions (i.e. that his equations are neither more nor less in number than
his unknowns). But when a great many symbols haveto be used,they become
verylaboriousto any one butthe writer himself. Andthough Cournot's genius
must give a new mental activity to everyone who passes through his hands, and
mathematiciansofcalibresimilartohis mayusetheirfavouriteweaponsin
clearing a way for themselves to the centre of some of those difficult problems
of economic theory, of which only the outer fringe has yet been touched; yet it
seemsdoubtfulwhetheranyonespendshistimewellinreadinglengthy
translations ofeconomic doctrinesinto mathematics,that have not been made
byhimself. Afewspecimensofthoseapplicationsof mathematicallanguage
whichhaveprovedmostusefulformyownpurposeshave,however,been
added in an Appendix.
September, 1890.