373
T H E O R I A
eISSN 0495-4548 – eISSN 2171-679X
Some imes you ide he Pegasus, some imes you ake he oad:
Mi chell on laws in biology
(Unas eces mon as a Pegaso, y o as eces as po ca e e a: Mi chell sob e leyes en biología)
Anya Plu ynski*
Washing on Uni e si y in S . Louis
ABSTRACT: Mi chell’s philosophical con ibu ions a e pa o an ongoing con e sa ion among phi-
losophe s and scien is s abou laws and uni ica ion in biology, going back a leas o Da win. This a icle
si ua es Mi chell in his con e sa ion, explains why and how she has co ec ly guided us away om alse
idols, and engages se e al di icul ques ions she lea es open. I a gue ha he e a e di e en epis emic
oles laws (o models desc ibing lawlike egula i ies) play in biological inqui y. Fi s , hey play he ole o
“how possibly” explana ions, akin o He schel’s cha ac e iza ion o Whewell’s “a p io i Pegasus,” and sec-
ond, hey p o ide desc ip ions o empi ical egula i ies, akin o he “plain ma e o ac oads e .”
KEYWORDS: laws, uni ica ion, in eg a ion, explana ion, p edic ion, biology.
RESUMEN: Las con ibuciones ilosó icas de Mi chell son pa e de una con e sación en cu so en e ilóso os
y cien í icos sob e las leyes y la uni icación en biología, que se emon a al menos a Da win. Es e a ículo si úa a
Mi chell en es a con e sación, explica po qué y cómo nos ha alejado co ec amen e de los alsos ídolos y abo da
a ias p egun as di íciles que deja abie as. A gumen o que hay di e en es oles epis émicos que juegan las leyes
(o modelos que desc iben egula idades legali o mes) en la in es igación biológica. En p ime luga , desem-
peñan el papel de explicaciones de “cómo es posible”, simila es a la ca ac e ización de He schel del “Pegaso
ap io i” de Whewell, y en segundo luga , p opo cionan desc ipciones de egula idades empí icas, simila es al
“simple caballo de lab anza de las cues iones de hecho”.
PALABRAS CLAVE: leyes, uni icación, in eg ación, explicación, p edicción, biología.
* Co espondence o: Anya Plu ynski. Washing on Uni e si y in S . Louis, Depa men o Philosophy, One B ookings D i e, S . Louis
(MO63130U.S.A.)– [email p o ec ed]– h ps://o cid.o g/0000-0003-3791-7720
How o ci e: Plu ynski, Anya (2023). «Some imes you ide he Pegasus, some imes you ake he oad: Mi chell on laws in biology»; Theo ia. An
In e na ional Jou nal o Theo y, His o y and Founda ions o Science,38(3), 373-388. (h ps://doi.o g/10.1387/ heo ia.23963).
Recei ed: 2022-10-08; Final e sion: 2023-04-02.
ISSN0495-4548 - eISSN2171-679X / © 2023 UPV/EHU
This wo k is licensed unde a
C ea i e Commons A ibu ion-NonComme cial-NoDe i a i es 4.0 In e na ional License
Theo ia, 2023, 38(3), 373-388
h ps://doi.o g/10.1387/ heo ia.23963
Anya Plu ynski
374 Theo ia, 2023, 38/3, 373-388
1. In oduc ion
Mos philosophe s o biology w i ing oday on he na u e o explana ion o heo y change
in biology seem o be mo e conce ned wi h causa ion, mechanism, models, and idealiza ion
han laws, and a mo e conce ned wi h “in eg a ion” han “uni ica ion” (see, e.g., Ande -
sen, 2014a, 2014b, B ailla d & Mala e e, 2015; B igand , 2015; Po ochnik, 2017). Indeed,
some see alk o laws o uni ica ion in biology as o ma ginal, o pe haps only his o ical in-
e es . Why? Pa o he answe will equi e a close (bu b isk) look a biology i sel . Pa ,
howe e , has o do wi h a con e sa ion among philosophe s and scien is s abou laws and
uni ica ion in biology, going back a leas o Da win. Mi chell’s (1997, 2000, 2002 2003a,
2003b, 2009) wo k has played an impo an ole in his ongoing con e sa ion. In my iew,
Mi chell has co ec ly guided us away om alse idols, hough she also lea es some in e es -
ing and di icul ques ions open. Thus, he wo cen al aims o his pape a e i s , o si u-
a e Mi chell’s iews in his his o ical con e sa ion, and second, o poin o, and begin o ad-
d ess, hese open ques ions. The con e sa ion begins, a guably, wi h Da win.1
2. Back o he En angled Bank
In he inal pa ag aph o he O igin, Da win w o e:
I is in e es ing o con empla e a angled bank… and o e lec ha hese elabo a ely con-
s uc ed o ms, so di e en om each o he , and dependen upon each o he in so complex a
manne , ha e all been p oduced by laws ac ing a ound us. These laws, aken in he la ges sense,
being G ow h wi h ep oduc ion; Inhe i ance which is almos implied by ep oduc ion; Va ia-
bili y om he indi ec and di ec ac ion o he condi ions o li e, and om use and disuse; a Ra-
io o Inc ease so high as o lead o a S uggle o Li e, and as a consequence o Na u al Selec ion,
en ailing Di e gence o Cha ac e and he Ex inc ion o less imp o ed o ms. Thus, om he
wa o na u e, om amine and dea h, he mos exal ed objec which we a e capable o concei -
ing, namely, he p oduc ion o he highe animals, di ec ly ollows. … whils his plane has gone
ci cling on acco ding o he ixed law o g a i y, om so simple a beginning endless o ms mos
beau i ul and mos wonde ul ha e been, and a e being e ol ed.
Why was Da win so conce ned o cha ac e ize his gene aliza ions ega ding pa e ns o in-
he i ance, a iabili y, and g ow h as “laws”? Wha was he signi icance o his compa ison o
hese ( a he less secu e) gene aliza ions o he law o g a i y?
Cha ac e izing hese pa e ns as laws was a delibe a e choice, and a key he o ical mo e
o Da win’s (see, e.g., Hull, 1972, 1973, 1983, 2003; Ruse, 1975, 1979). He schel was one
o he i s philosophe s o science, and Da win had ead He shel’s philosophical wo k on
he na u e o scien i ic inqui y. So, he knew ha He schel ook New on o be exempla y;
in pa icula , he knew ha He schel iewed New on as exempla y because o his iden i i-
ca ion o law ul egula i ies, es ing on obse a ions o “ ue causes,” and his uni ica ion o
celes ial and e es ial physics. Da win a gues ha hese laws o a ia ion, ep oduc ion
1 Though I could ha e chosen many o he scien i ic igu es o begin, I hope i will become clea soon
why Da win is such an ap choice.
h ps://doi.o g/10.1387/ heo ia.23963 375
Some imes you ide he Pegasus, some imes you ake he oad: Mi chell on laws in biology
and g ow h a e ue causes. Mo eo e , he a gues ha i hey a e in ope a ion, we can see as
consequence how he s uggle o exis ence, and hus na u al selec ion, can come abou .
I was he la e “hypo hesis” ha caused He schel o balk. While He schel and Wil-
liam Whewell (among he mos in luen ial philosophe s o he 19 h Cen u y) ag eed ha
New on was an exempla y scien is , hey di e ed abou why, and o e ed i al iews abou
he cen al me hods o science. He schel was c i ical o Whewell’s celeb a ion o consil-
ience o induc ions, o “jumping oge he o ac s,” wha we oday migh call in e ence o
he bes explana ion. In his e iew o Whewell’s massi e mul i olume ome, A His o y o
he Induc i e Sciences (1840), He schel c i icized Whewell’s championing o me hods ha
he conside ed less cau ious han he us ed pa h he imagined ue scien is s ough o ake:
“The high a p io i Pegasus… a noble and gene ous s eed who bounds o e obs acles which
con ine he plain ma e o ac oads e o a die pa hs and a longe ci cui .” (He schel,
1841, p. 223)
F om his eading o He schel, Da win unde s ood ue science o in ol e he disco -
e y o laws ia “induc i e me hods,” and in he O igin, he pains akingly eco ded obse -
a ions he and many o he s had made o pa e ns o inhe i ance, a iabili y, and g ow h.
Cha ac e izing hese pa e ns as “laws” was a delibe a e choice, as was he e e ence o g a -
i y.2 Following New on’s example was —by he ligh s o bo h He schel and Whewell— he
ma k o ma u e science. Despi e Da win’s choices, howe e , He schel and Whewell we e
bo h skep ical o Da win’s heo y. Indeed, He schel pu po edly called na u al selec ion
he “law higgledy piggle y.” Why?
He schel himsel ne e made clea wha he mean , bu he e a e ample easons o e ed
up in he li e a u e (see, e.g., Hull, 1972, 1973; Ruse, 1975, 1979; Hodge, 1977, 1991,
1992; Pence, 2018; Honenbe ge , 2018). Fi s , Da win’s pu po ed “laws” o g ow h and
ep oduc ion, inhe i ance, a iabili y, e c., a e no excep ionless. O ganisms only end o
g ow o esemble hei pa en s, no el a ian s a ise wi h some egula i y, bu no in a p e-
dic able way (as Da win said, “by chance”), and no all popula ions expand a a “geome ic”
a e. No a e all esou ces s ic ly “a i hme ical” in hei limi a ions. Mo eo e , Da win
only a gues ha i hese condi ions hold —i o ganisms a y, i a ia ion is inhe i ed, and i
esou ces a e limi ed— hen compe i ion will lead o na u al selec ion, and in u n, he di-
e gence o cha ac e , and adap a ion. S ikingly, Da win does no desc ibe na u al selec-
ion pe se as a law, bu a consequence, o “ esul ,” “en ailed,” by he gene al law ul egula i-
ies he desc ibes. He g an s ha hese condi ions a e no always me .
So, Da win’s a gumen was a combina ion o wha migh pe haps be desc ibed as gen-
e aliza ion by induc ion, and in e ence o he bes explana ion. Da win’s “i - hen” claim
was he co e o his a gumen in he O igin, bu he also a gues o na u al selec ion as he
bes a ailable explana ion o di e gence, biogeog aphy, o ganisms’ s unning i wi h hei
en i onmen , he ossil eco d, and he many simila s uc u al ea u es and de elopmen al
p ocesses among species. O a leas , he a gues ha his explana ion is mo e p obable han
special c ea ion. Da win’s easoning, in o he wo ds, was no demons a i e. No su p is-
2 Thanks o a e iewe o his u he in o ma ion: Hodge has no ed ha Da win had indeed consid-
e ed a “lawlike” p og am o biology in analogy o New on bu abandoned he “laws o li e” o mu-
la ion in his ea ly no ebooks. Ano he eading o he same passage has “law” playing a ole mo e like
“seconda y cause” han “New onian law,” echoing he in oca ions o seconda y causes (and hei com-
pa ibili y wi h di ine design) ha Da win added o he O igin’s on ispiece.
Anya Plu ynski
376 Theo ia, 2023, 38/3, 373-388
ingly, hen, He schel was c i ical; and he was no alone. Many c i ics o Da win (e en some
o Da win’s “champions”) a gued ha he had a bes shown ha his explana ion was plau-
sible.
Da win’s “laws” lacked he uni e sali y o New on’s heo y o g a i y. New on him-
sel hough o laws o na u e as exp essions o God’s plan. On such a iew, he laws o na-
u e canno come o be, o cease o be. P esumably, God’s laws a e ixed and unchanging
e idence o his p o idence and bene olence, uni e sal and necessa y. Many candida es o
“biological laws” lack his cha ac e : hey a e ei he con ex -dependen , p obabilis ic gen-
e aliza ions abou sys ems ha a e hemsel es p oduc s o his o y (and, could hemsel es
change i a ious condi ions a ise), o hey a e simila o Da win’s “i - hen” claims, desc ib-
ing en ailmen s om se s o ini ial condi ions (many o which a e ei he p obabilis ic, o ,
puzzlingly, sys ema ically iola ed). This has led o a las ing deba e bo h abou laws, hei
ole in biology, and he s a us o biology as science.
3. Si ua ing Mi chell
To si ua e Mi chell’s ole in he ongoing con e sa ion abou laws in biology, i ’s i s im-
po an o be clea abou wi h whom she is in dialogue. Mi chell’s con ibu ion o he
con e sa ion was, a guably, shaped by he ecen U.S. social con ex in which bo h e o-
lu iona y biology and philosophy o biology, de eloped. Philosophy o biology as a disci-
pline a ose in he mid- wen ie h Cen u y, when logical empi icism was declining om i s
peak, and (a leas in he U.S.) he s a us o e olu iona y biology as a science was con es ed
in legal dispu es o e he eaching o e olu ion in public schools.3 So, many philosophe s
o biology ook upon hemsel es he ask o bo h de ining a ield o s udy and explaining
and de ending e olu iona y biology as a science. As a esul , many philosophe s o biology
(Mi chell included) ei he ained as, o collabo a ed wi h scien is s, and much o he phil-
osophical wo k on biology engages wi h concep ual and me hodological deba es ha a ose
in scien i ic p ac ice. Fo ins ance, philosophe s o biology ha e con ibu ed o deba es
among scien is s abou species, i ness, le els and uni s o selec ion, and adap a ionism.
Mi chell’s wo k is a i id example o his engagemen .
Mi chell and o he philosophe s o biology b ough a en ion o some impo an ac s
abou he dis inc i e subjec ma e and p ac ice o biological science. Biologis s deal wi h
li ing hings on ea h, he exis ence and cha ac e o which is bo h his o ically con in-
gen , and gene aliza ions abou a e o en highly con ex dependen . So, o achie e some-
hing e en app oaching claims ha ha e he cha ac e o “na u al necessi y” in biology, bi-
ologis s will o en ake hings o be ixed ha hey know o a y. I he e a e any hing like
“necessa y” u hs in biology, hey a e u hs ha hold unde condi ions ha a e highly ide-
alized; ha is, hey a e ue only in ci cums ances ha a ely (i e e ) hold. Indeed, some
such “ u hs” hold only o impossible wo lds – in ini e popula ions, o o ganisms li ing
in unchanging en i onmen s. Ye , biologis s seem ake se e al such u hs o play impo -
an oles in ou unde s anding o biological sys ems and hei e olu ion. Many unc ion as
3 Fo u he discussion o he his o y o philosophy o biology, see, e.g., Ruse, 2018; Mala e e e al.,
2020. Thanks o a e iewe o hese sugges ions.
h ps://doi.o g/10.1387/ heo ia.23963 377
Some imes you ide he Pegasus, some imes you ake he oad: Mi chell on laws in biology
“as i ” o ganizing amewo ks o biological esea ch, o pe haps, as se ing ou limi condi-
ions, o null models, agains which we can es hypo heses o de elop explana ions.4
While he na u e o biology and biological science is essen ial o esol ing any deba es
abou laws in biology, he e has also been a long con e sa ion among me aphysicians con-
ce ning he na u e o he commi men s o ou bes scien i ic heo ies. While logical empi -
icis s sough o p omo e ela i ely me aphysically ee science, mo e ecen ly, philosophe s
ha e been mo e willing o conside laws o na u e as cen al o science. Se e al philosophe s
ha e aken me aphysical ques ions o u n on whe he we ough o ea laws, o ins ance,
as in some sense undamen al, o pe haps ins ead, uni e sals, p ope ies, o disposi ions
(Lewis, 1983; A ms ong, 1978, 1983). Mi chell, and mos o he philosophe s o biology,
we e only indi ec ly engaged wi h such con e sa ions. Why? The e is a dis inc i e empi -
icism and p agma ism a play in much o Mi chell’s wo k, and indeed, he wo k o many
philosophe s o biology. Thus, many philosophe s o biology do no engage wi h he ques-
ions ha puzzle many me aphysicians (should we be Humean abou laws, e c.). Such de-
ba es do no seem o ca y any clea implica ions, o help esol e, he as majo i y o con-
cep ual o me hodological deba es ha a ise in he biological sciences. Ye , as I sugges ed
ea lie : a cen al goal o much o he philosophical engagemen wi h he biological sciences
in Mi chell’s wo k has been esol ing concep ual and me hodological ques ions ha a ise
in he p ac ice o science (see, e.g., Mi chell, 1997, 2000, 2003, 2009).
Ques ions abou he ela i e s abili y o causal gene aliza ions, and he aim and me h-
ods o in eg a i e esea ch, do a ise in scien i ic p ac ice. Mo eo e , conce ns abou hese
ma e s shape p ac ical ma e s such as law and policy conce ning mi iga ing he e ec s
o clima e change, p ese a ion o endange ed species, and clinical medicine. Fo example,
clinical in e en ion equi es ha one say wha cause-e ec ela ionships a e ela i ely s a-
ble, gi en backg ound condi ions ha hemsel es a y. The ac o he ma e is we o en
canno know which such backg ound condi ions a e in place, making p ognosis and ea -
men eno mously di icul . In ligh o ou epis emic limi a ions, and in ligh also o he dis-
inc i e complexi y and con ingency o biology, Mi chell has a gued, he line be ween law
and acciden in biomedicine is no a sha p one (Mi chell, 1997, 2000). So oo, no coinci-
den ally, is he line be ween “na u al” kinds and na u al enough o a gi en pu pose (p e-
dic ion, in e en ion, e c.).
These obse a ions —abou bo h he complexi y and con ingency o biology— ha e
been a cen al ocus o Mi chell’s wo k. Ye , his con ingency has led many o be skep ical
o biology’s s a us as a science, s a ing, as we’ e seen, wi h he ecep ion o Da win’s he-
o y. Thus, Mi chell’s wo k has engaged a a ie y o audiences: no only philosophe s, bu
also scien is s misin o med by logical empi icis ideals o science, and he public. To he ex-
en ha alse p esupposi ions abou he na u e o science in o m p ac ical conce ns, like
he eaching o biology in public schools, add essing such ma e s is impo an . And a leas
one such cen al p esupposi ion is ha scien is s ough o aim a law ul desc ip ions o he
wo ld. Le us u n now o he de ails o he philosophical deba e his si ua ion has gene a ed.
4 Mi chell was no he only one o no ice hese ac s abou biological p ac ice. Fo u he discussion
o simila iews, see also, e.g., Lewon in, 2000; Wimsa , 2007; God ey-Smi h, 2006, 2009. Some
‘i - hen’ hypo he icals do he wo k o null models, equilib ium condi ions, o limi cases, wha Bill
Wimsa desc ibes as “ alse models”.
Anya Plu ynski
378 Theo ia, 2023, 38/3, 373-388
4. Laws? We don’ need no s inking laws!
Many biological gene aliza ions a e a he signi ican , and p ac ically ele an o science,
medicine, and law and policy, bu we do no gi e hem he hono i ic s a us o “laws.” Mos
o us would no say i is a law o na u e, o ins ance, ha smoking causes lung cance , o
ha ex inc ion is mo e likely in small, isola ed popula ions. Bu bo h a e so well es ablished
ha hey a e used o suppo ede al laws and policies ha go e n he ad e isemen o cig-
a e es, and he p o ec ion o endange ed species. Why hen do we no call hem laws? Phi-
losophe s o biology con on ing hese ma e s ha e aken one o se e al app oaches. Some
se ou no ma i e c i e ia o laws o na u e, and ei he claim ha biology ails o mee
hem, o mee s hem in spades. O he s esis se ing ou necessa y and su icien no ma i e
c i e ia o he s a us o laws in science. Mi chell’s wo k is an example. Indeed, he wo k e-
ames he con e sa ion a ound laws. Ins ead o conce ning ou sel es wi h wha laws “a e”
(o wha c i e ia hey “mus ” mee ), she a gues, we should a end o wha laws “do.” Tha
is, she is conce ned wi h he p agma ic and epis emic oles o laws, o lawlike gene aliza-
ions in biology. Below, I gi e a b ie o e iew o some o he al e na i e iews in he philo-
sophical li e a u e, si ua ing Mi chell’s wo k in his con e sa ion.
G asping he i s ho n (a he no ma i e end o he spec um), many philosophe s
ha e assumed ha wha is dis inc i e abou laws o na u e is hei cha ac e as empi ical,
uni e sal, and “necessa y” gene aliza ions. Such c i e ia a e assumed o be me in phys-
ics; and some ha e a gued ha while laws in physics mee he no ma i e c i e ia o law-
ulness, gene aliza ions in biology do no (Sma , 1963; Schi e , 1991; Bea y, 1995; Ea -
man& Robe s, 1999; Woodwa d, 2000, 2001, 2002, 2003; Ea man e al., 2002). O he s
a gue ha he e a e wo kinds o laws, ce e is pa ibus laws and s ic laws, and ha only he
o me a e ound in he “special sciences” (e.g., biology, an h opology, psychology) (Fodo ,
1991; Hausman, 1992, pp. 133-151; Pie oski & Rey, 1995). O he s s ill de end a weake
se o condi ions on lawhood and say ha laws in biology mee such condi ions (Sobe ,
1997; Elgin, 2003).
Mi chell’s wo k is an uncom o able i wi h his dialec ic. Ra he han se ou no ma-
i e c i e ia o lawhood, she akes a dis inc i ely p agma ic iew in his discussion. Fi s ,
she a gues ha any accoun o laws and hei ole in he biological sciences ough o s a
wi h a close examina ion o scien i ic p ac ice. Ou ques ion should no be whe he laws
mee ideal c i e ia, bu ins ead: Wha unc ion o ole do candida e biological laws play in
inqui y?5 Second, s a ing wi h close a en ion o p ac ice, Mi chell no es ha he e a e a
a ie y o dimensions along which candida e laws a y – in s eng h, and s abili y, o in-
s ance. In pa on hese empi ical g ounds, Mi chell a gues ha he e is no ha d and as
line o d aw be ween pu po edly law ul gene aliza ions and acciden al egula i ies. While
such iews may seem con o e sial, a close look a he his o y o deba es o e laws in bi-
ology (along wi h a ca e ul look a he ac ual biological sciences, g an ing we should ake
science i sel se iously as a (de easible) sou ce o e idence in any such deba e), sugges s
5 The e is a g ea deal mo e o say abou he na u e o p agma ism and i s in luence in philosophy o sci-
ence, and he ways in which Mi chell exempli ies a p agma ic app oach o philosophy o science. Su -
ice i o say ha add essing his ques ion in any dep h would equi e a pape by i sel . Fo u he dis-
cussion, I ecommend he ollowing o hcoming: The P agma is Challenge: P agma is Me aphysics
o Philosophy o Science edi ed by H. K. Ande sen and Sand a D. Mi chell (2023).
h ps://doi.o g/10.1387/ heo ia.23963 379
Some imes you ide he Pegasus, some imes you ake he oad: Mi chell on laws in biology
o he wise. Indeed, in many ways, he posi ion seems he mos de ensible one a ailable. To
explain, I will highligh se e al au ho s I ake Mi chell o be engaging wi h di ec ly: Bea y,
Sobe , and Lange.
In Bea y’s iew, all gene aliza ions in biology a e ei he (a) ma hema ical, physical, o
chemical gene aliza ions, o (b) dis inc i ely biological, in which case, con ingen . Bea y’s
a gumen is as ollows:
— Dis inc i ely biological gene aliza ions desc ibe e olu iona y ou comes.
— E olu iona y ou comes a e con ingen s a es o a ai s; hey could ha e been o he -
wise, and so do no “p osc ibe” wi h necessi y.
— Any appa en ly non-con ingen laws o biology u n ou o depend o hei “neces-
si y” on ma hema ics, chemis y, o physics.
— Laws o na u e mus be ue, empi ical (no ma hema ical), and “necessa y” in he
sense o p osc ibing wha ’s possible.
— Biology’s “lawlike” gene aliza ions a e ou inely iola ed.
— The e o e, he e a e no “laws” o biology.
While Mi chell ag ees wi h Bea y ha wha na u al selec ion yielded may be undone, and,
ha e olu ion can lead o di e en ou comes om he same s a ing poin , she disag ees
wi h his conclusions. The easons why a e as ollows. Fi s , she dispu es he no ma i e c i-
e ia o laws ha his pic u e p esupposes; namely, ha laws need be uni e sal, le alone
“necessa y,” a he han con ingen p oduc s o his o y. While many philosophe s ha e as-
sumed ha laws in physics a e uni e sal, o he s s ill dispu e his (Ca w igh , 1983; Gie e,
1999). Many g an ha physical laws hold only gi en some condi ions ha es ic hei
scope, and hese ce e is pa ibus condi ions do no p e en laws om doing explana o y and
p edic i e wo k. Thus, ha dis inc i ely biological phenomena a e o en only ue “ce e is
pa ibus,” o (in Mi chell’s e ms) a e only ( ela i ely) s able gene aliza ions, i doesn’ nec-
essa ily ollow ha hey canno unc ion in he same way as physical laws.
Tha said, Mi chell ag ees wi h Bea y ha we should expec and indeed seek a plu al-
i y o mechanisms and causes in biology. Sea ching o a “uni ied” heo y in biology ( he
New onian ideal) is p oblema ic exac ly because he same biological unc ion can be eal-
ized in di e en ways. Indeed, mul iple ealiza ion is i sel a p ope subjec o in es iga ion
o biology; biologis s wan o unde s and how and why di e en o ganisms ha e achie ed
he “same” unc ion, and hey do so by in es iga ing di e en mechanisms, and e olu ion-
a y and de elopmen al his o ies unde pinning his “same” unc ion. The uni ica ionis pic-
u e p esupposes ha laws a each le el can be educed o, o explained in e ms o , law ul
egula i ies a some lowe le el. Bu , in biology, he e a e biological gene aliza ions abou
pa e ns and p ocesses a one empo al and spa ial scale ha canno be educed o gene al-
iza ions a o he scales, ce ainly no ia deduc i e subsump ion. Thus, he p esupposi ion
mo i a ing a uni ica ionis pic u e o science (a leas o he deduc i e subsump ion kind)
is unde mined (see, e.g., Mi chell, 2000, 2003).
Wha so s o (lawlike) gene aliza ions a e he e? He e, i may help o jux apose
Mi chell wi h Ma c Lange. Lange (2005) a gues ha laws in biology (and o he special
sciences) desc ibe s able coun e ac ual gene aliza ion, ela i e o some se o backg ound
condi ions ha ( o he pu poses o he scope o ha discipline) can be ega ded as con-
s an . Fo example, o he pu poses o es ablishing lawlike gene aliza ions in ecology, ecol-
ogis s ea as assump ions ha he sun will no die ou , and he seasons will be ( ela i ely)
Anya Plu ynski
380 Theo ia, 2023, 38/3, 373-388
egula . Lange’s idea is ha he gene ali y o special science laws is always ela i e o a do-
main speci ic se o coun e ac ual possibili ies ypical o ha home discipline.
In o he wo ds, Bea y, Mi chell, and Lange all ag ee ha candida es o law in biol-
ogy a e con ingen u hs bu disag ee abou he way in which hey a e con ingen , and,
whe he he e is any sha p dis inc ion o be made be ween laws and acciden s. Bea y sees
he con ingency o e olu iona y biology as su icien o ule ou laws in biology. In con-
as , Mi chell, and Lange g an ha his o ically acciden al gene aliza ions can well coun
as laws; (indeed, e en many physical laws ha we ea as “necessa y” may well ha e been
o he wise). Mi chell sees di e en dimensions o coun e ac ual in a iance as ma e s o
deg ee, whe eas Lange d aws a sha p dis inc ion be ween s able and uns able se s ( o he
pu poses o a gi en scien i ic ield). Lange con ends ha he special scien is s ca e ou
a ange o hypo he ical ci cums ances ha ( o he pu poses o a gi en ield), allow us o
say wha holds (o close enough) unde all possible condi ions, come wha may, no ma e
wha , e c.
Who is igh ? On he one hand, I ag ee wi h Lange ha we could (in p inciple) iden-
i y such discipline speci ic se s o laws – o u hs ha hold (come wha may) gi en back-
g ound ci cums ances we ake o be su icien ly s able. In p ac ice, howe e , disciplina y
bounda ies a e luid, lawlike egula i ies a e bo owed and edeployed by neighbo ing
ields, and o suppose ha we could iden i y all ele an backg ound condi ions o which
he laws o a discipline a e su icien ly s able is, o say he leas , somewha o an idealiza-
ion. S abili y is, a e all, o en a ma e o deg ee, and his is especially so when mo ing be-
ween clima es, and ime scales. Fo p ac ical pu poses, all law-like gene aliza ions in biol-
ogy a e bo h “con ingen ” in he sense o his o ically con ingen on ai s and mechanisms
ha e ol ed, and con ingen on a a ie y o backg ound condi ions, many o which we may
well be unawa e o . While in p inciple he e a e law ul gene aliza ions ha hold, p o ided
we hold ce ain condi ions s able, we o en simply don’ know all he condi ions equi ed
o he law o coun as nomically s able, by Lange’s ligh s. This is why (o en) he bes we
can do is ep esen he wo ld as i hey do. Indeed, many “i - hen” gene aliza ions like Da -
win’s ega ding na u al selec ion ha e his la o : “i hese gene al egula i ies hold, hen we
should expec …” (in Da win’s case, na u al selec ion).6
He e I hink i is wo h u ning o Sobe , ano he in e locu o in his ongoing con e -
sa ion. Sobe a gues ha e olu iona y biologis s de i e “i - hen” gene aliza ions ha ha e
simila p ope ies o laws ( hey a e used in p edic ion and explana ion). E olu iona y he-
o y desc ibes bo h he “sou ces” and “consequences” o he causes o e olu ion. “Sou ce
laws” desc ibe gene al ecological ela ions be ween o ganisms and en i onmen s. “Conse-
quence laws” desc ibe he consequences o hese ela ions o e olu ion. In many ways, his
dis inc ion uns pa allel o he dis inc ion be ween wha Da win himsel calls “laws” e sus
“consequences.” By way o example, Sobe a gues ha he gene aliza ion “he e ozygo e su-
pe io i y ends o p omo e s able polymo phisms” is a consequence law. O e dominance
( he selec i e ad an age ha acc ues o he e ozygo es in some en i onmen s) leads o s a-
bilizing selec ion ha main ains bo h alleles in a popula ion (all else being equal). Tha
is, unde condi ions o he e ozygo e supe io i y, allele equency con e ges o an equilib-
6 Lange could espond he e by a guing ha he kind o lexibili y ha is p esen in Mi chell’s iew can
be sa ed on his iew by ine g aining he “sciences” a issue. Thanks o a e iewe wi h his sugges ion.
h ps://doi.o g/10.1387/ heo ia.23963 381
Some imes you ide he Pegasus, some imes you ake he oad: Mi chell on laws in biology
ium alue o 50:50, i espec i e o he ini ial equency o he ele an alleles. Sobe ex-
plains how his kind o “i - hen” claim is de i ed: “When biologis s speci y a model o a
gi en kind o p ocess, hey desc ibe he oles by which a sys em o a gi en kind changes.
Models ha e he cha ac e is ic i / hen o ma ha we associa e wi h scien i ic laws. These
ma hema ical o malisms say wha will happen i a ce ain se o condi ions is sa is ied by a
sys em. They do no say when, o whe e, o how o en hose condi ions a e sa is ied in na-
u e.” (Sobe , 1993, p. 16)
Sobe ’s cha ac e iza ion o “laws” equi es us o esis some ea u es o “ adi ional”
concep ions o law bu sa is ies o he s. I ells us wha (all else being equal) will ensue,
much like Da win’s “i - hen” condi ional in he O igin. To be su e, wha such “i - hen”
condi ionals desc ibe is o en a highly idealized ci cums ance; in his case, we mus assume
ha no o he ac o s han na u al selec ion o his he e ozygo e ype a e a wo k in a gi en
popula ion – no coun e ailing selec ion o o he ai s, no mig a ion, o d i , o he e -
ec s o sampling e o , on he dis ibu ion o gene equencies. The models Sobe is de-
sc ibing gi e us some hing like “necessi y,” p o ided such condi ions hold. Fo ins ance,
unde he p esupposi ions abo e ega ding o e dominance, a 50:50 dis ibu ion o alleles
would necessa ily come abou (e en hough such condi ions may ne e be me !). Some-
imes Sobe seems o sugges ha he condi ions o he model need ne e be me o he
i - hen gene aliza ion o be ue. Sobe gi es he example o he Ha dy-Weinbe g heo em
and compa es i o a p oposi ion abou coin ossing.
The e is some hing igh abou his, and some hing w ong. Ha dy-Weinbe g is a he-
o em, which s a es ha , i a popula ion mee s ce ain condi ions, i will be in equilib ium.
Theo ems a e (by de ini ion) necessa y u hs. Bu hey a e no me ely “ma hema ical”
u hs; hey a e no ue only in i ue o he u hs o ma hema ics. Ra he hey a e (o
would be) ue any sys em in which he condi ions o he model hold. Ha dy-Weinbe g’s
equa ion is a desc ip ion o a sys em whe e popula ions a e in ini e. The e a e no in ini e
popula ions. Howe e , we can (and do) use he heo em o de i e empi ical claims abou
how popula ions a e in ac (i.e., empi ically) subjec o, e.g., mu a ion, selec ion, o d i .
Tha is, he model se es as a “null” model, which biologis s use o de i e empi ical hypo h-
eses abou he a ious ways in which popula ions depa om he condi ions se ou in he
model.
Many heo ems in biology —and e olu iona y heo y in pa icula — ha e his cha -
ac e . Fo ins ance, in 1930, Fishe o mula ed he Fundamen al Theo em o Na u al Se-
lec ion: ‘ he inc ease o a e age i ness o he popula ion asc ibable o a change in gene e-
quency . . . is equal o he gene ic a iance in i ness’ ([1930], p. 377). He compa ed his
undamen al heo em o he second law o he modynamics, and claimed i p o ided he
undamen al basis o e olu iona y change. Ye , he sho ly he ea e ema ked on how
his gene aliza ion is sys ema ically iola ed, namely, whe e en i onmen s a e in lux. As
Okasha poin s ou , his only means ha he FTNS “p ope ly unde s ood” is ue, gi en
Fishe ’s quali ica ion “’due o na u al selec ion in a cons an en i onmen ’... Wi hou he
quali ica ion he FTNS is simply un ue — o i implies ha selec ion mus always d i e
he a e age popula ion i ness up, which… is alse” (Okasha, 2008, p. 330). Wha unc ion
hen does such a alse claim abou an imagina y si ua ion se e? En i onmen s change all
he ime!
Like many such heo ems in heo e ical biology, he FTNS desc ibes he p econdi ions
on some pa e n o p ocess. Fishe ’s claim is ha any e olu iona y change by na u al selec-
Anya Plu ynski
388 Theo ia, 2023, 38/3, 373-388
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anya plu ynsKi is P o esso o Philosophy a Washing on Uni e si y in S . Louis, and a ilia ed acul y wi h
he Di ision o Biology and Biomedical Sciences. He esea ch is in he his o y and philosophy o biology
and medicine.
add ess: Washing on Uni e si y in S . Louis, Depa men o Philosophy, One B ookings D i e, S . Louis,
MO 63130, U.S.A. E-mail: [email p o ec ed] – ORCID: 0000-0003-3791-7720.
