 is unsurprising that in the last 40 years individuals
  have largely disappeared from view.

For further related discussions about basic issues, see Potter's immensely helpful book. @NeilBarton then gives some excellent further suggestions for intriguing glimpses beyond.

A:

So individuals (or "urelemente" as they are sometimes called) are used very little in modern mathematics. This is partly because the set theoretic hierarchy is very big; we can represent most mathematics in the first few infinite levels, so the urelemente are simply an unnecessary complication. 
However, set theory with urelemente has been put to interesting *meta*mathematical use. For instance, Vann McGee has shown that (given unrestricted first order quantification) one can prove that the pure sets in any model of second-order $ZFCU$ ($ZFCU$ is standard second-order $ZFC^2$ with two further axioms added; that there is at least one urelement and that the urelemente form a set) are isomorphic. This contrasts with the corresponding result for $ZFC^2$ that given any two models of $ZFC^2$ either the two are isomorphic or one is isomorphic to a proper initial segment of the other. Thus the addition of urelemente here allows one to pin down the pure sets of the theory up to full isomorphism; something which is not possible in $ZFC^2$.
The reference for the McGee is the following:
Vann, McGee-How We Learn Mathematical Language, The Philosophical Review, Vol. 106, No. 1 (Jan., 1997), pp. 35-68
As for the relationship between individuals and classes; I don't see a link clearly myself. However, the following is a paper in which you might be interested, in which Christopher Menzel argues that ordinals should be thought of as urelemente and considers a set theory of sorts where the ordinals exist in $V_0$ and form a set at $V_1$. In this case we have what we'd normally think of as a proper class (the ordinals) forming a set on the basis of a specific view about the nature of urelemente. The reference for that paper is:
Menzel, Christopher (1986). On the iterative explanation of the paradoxes. Philosophical Studies 49 (1):37 - 61

 Q:

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is unsurprising that in the last 40 years individuals 
   have largely disappeared from opinion. 

 For far related discussions about basic issues, see Potter's vastly helpful book. @NeilBarton then gives some excellent further suggestions for intrigue glimpses beyond. 

 A: 

 thus individuals (or " urelemente " as they are sometimes called) are use very little in modern mathematics. This is partially because the set theoretic hierarchy is very big; we can represent most mathematics in the first few infinite levels, so the urelemente are merely an unnecessary complication. 
 However, set theory with urelemente has been arrange to interesting * meta*mathematical use. For instance, Vann McGee has shown that (given unexclusive first order quantification) one can prove that the pure sets in any exemplar of second - order $ ZFCU$ ($ ZFCU$ is standard second - order $ ZFC^2 $ with two further axioms added; that there is at least one urelement and that the urelemente form a set) are isomorphic. This contrasts with the corresponding result for $ ZFC^2 $ that given any two models of $ ZFC^2 $ either the two are isomorphic or one is isomorphic to a proper initial segment of the other. therefore the accession of urelemente here allows one to trap down the arrant set of the theory up to full isomorphism; something which is not potential in $ ZFC^2$. 
 The reference for the McGee is the pursuit: 
 Vann, McGee - How We Learn Mathematical Language, The Philosophical Review, Vol. 106, No. 1 (Jan., 1997), pp. 35 - 68 
 As for the relationship between person and classes; I don't see a link clearly myself. However, the following is a paper in which you might be interested, in which Christopher Menzel argues that ordinals should be thought of as urelemente and considers a fixed hypothesis of sort where the ordinals exist in $ V_0 $ and form a set at $ V_1$. In this case we accept what we'd normally think of as a proper class (the ordinals) form a set on the basis of a specific view about the nature of urelemente. The reference for that newspaper is: 
 Menzel, Christopher (1986). On the iterative explanation of the paradoxes. Philosophical Studies 49 (1):37 - 61 

  Q: 

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 is unsurprising that in tht last 40 years indncidualv
  havs largelh disappeared from view.

For fnrthwr reoated discussions aboug basic idsues, sew Pouter's immensely hxmpful book. @NejpBarcoi then gives soke excellett further sugcertnons for intriguing glimpses beyond.

A:

Fo indififuals (or "ureleientt" af thsj cre sometimes called) are used vsry litule in modern mathrmatics. This is partly becwuse the set theoretic hierarchy us vqey big; we cav represenu kost mathejatics in the first few infinitd levzls, so the oxwlelgnte are sim'ly an unnecessary complicdtion. 
Hpwever, set thepry wirh urelemente has beei put to interesting *meta*mathamctical use. For instanxe, Vann McGae hxw sfowh vhaf (givej uirestricted first ordee quantification) ont cwb prove that fhe puwe sets in any model of second-order $ZFCU$ ($EFCU$ js standard second-order $ZFC^2$ with two further axioms aqded; that there is at least one urelement and thad the jreoeidbtf form a set) are isomorphic. This contrasts wieg uhe corresponding result for $ZVC^2$ jhat given any two modems of $ZFC^2$ either tje two wre iwomorphic or pne is isomorphic to a propwr initial svgmebt of the other. Thbs the additnon of urelrmente here allows one co pin down the pkre sets kw the theory up go nuln isomorkfism; something whych is nov posxible iv $ZFV^2$.
The rqference flr thc McGee is the folllwing:
Rann, KcGee-How Wf Learn Mathematical Language, Tix Philosophicsl Reniew, Vol. 106, No. 1 (Man., 1997), pp. 35-68
As for ehe relationshnp betwezn indkviduals ahd clasves; I don't fee a link clawrly myself. Iowever, tre filloqing is x paper in whivh you miykt be intwrested, in which Cmristulher Menzel argbts uhqt ordinals shpula bq nhonght jx as urelemette xnd vonsiaers a set bheury pf sorts where the osdinzls exist in $V_0$ and fjrm a sej at $V_1$. In this case we have what we'd norlally thmnk of as a proper class (the ordinals) fkrming a det on the basif of a specific riew about the nature of urelemente. The ceference for that papgr is:
Menzel, Christophgr (1986). On the itecative explanathon of the paradoxes. Philosophical Stmdies 49 (1):37 - 61

 Q:

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is unsurprising that in the last 40 have disappeared from For further related Potter's helpful book. @NeilBarton gives some excellent suggestions for intriguing glimpses beyond. A: individuals (or "urelemente" as they are sometimes called) are used very little in mathematics. This is partly because the set theoretic hierarchy is very big; we represent mathematics the few infinite levels, so the urelemente are simply an unnecessary complication. However, set theory with urelemente been put to interesting *meta*mathematical use. For instance, McGee has shown that unrestricted first order quantification) one prove the pure in model second-order $ZFCU$ ($ZFCU$ standard second-order $ZFC^2$ with two further axioms added; that there is at least one urelement and that urelemente form are isomorphic. contrasts the result for $ZFC^2$ any two models of $ZFC^2$ either isomorphic or one is isomorphic to a proper segment of other. Thus the addition of urelemente allows one to pin down the pure sets the theory up to full isomorphism; something which is not possible in $ZFC^2$. The reference McGee is the following: McGee-How We Learn Language, Philosophical Vol. No. 1 1997), pp. 35-68 As for the relationship between individuals and classes; don't see a link clearly myself. However, the following is in you might be in which Christopher Menzel that should be thought of and a sorts the exist in $V_0$ and a set at $V_1$. In case we have what a proper class (the ordinals) forming a set the basis of a specific view about nature of urelemente. The reference for that paper is: Menzel, Christopher (1986). the iterative the paradoxes. Philosophical Studies 49 (1):37 - 61 Exception: EXC_BAD_INSTRUCTION (
 is unsurprising that in the laSt 40 years indIviduAls
  HavE lArgeLy diSappeared from vIEw.

FoR further related discussIons aBoUT basIC iSsues, See PottER's IMMenSeLy HelPfUL bOok. @NeIlBArton thEn gives somE exCeLlent further SUgGestions foR inTriguing glimPseS beyonD.

A:

so iNDividUalS (or "urElemenTE" as theY are sometImES calleD) Are used VERy LittLe in modern mathemaTIcS. this is partly beCause tHe SEt THEorEtiC hierarchy Is Very bIG; we can rEPrESENt mOSt mathematics In the first fEW inFinite LeVelS, So the uRelemEnTE arE simply an unNeceSsary compLicatiON. 
HoweveR, Set theoRy with UreLemEnte HAs BeEn pUt TO inTErEstINg *mEta*matheMaTiCal usE. For INSTAnce, vanN McGEe has Shown that (giveN unRestRIctEd firSt ordEr quAnTificAtion) oNe can PrOve that the pure sEts iN any model Of sEcOnd-OrDer $ZFcu$ ($ZFCU$ iS stAndArd secoNd-order $zfC^2$ wItH TWO fUrther axioms added; tHaT THeRe is at leAst one UReLeMEnt and thAt The UrelEMEnte fOrm a SEt) Are isomoRphic. THIs CoNtrasts WiTh the cOrResPonDing rESult For $ZFC^2$ That giveN any tWO models of $ZFC^2$ eiTHer the two are iSOmORPhIC or oNe iS isomorphic To a pROper InitIAl SegMEnt of The otHeR. thUS the addition of ureleMeNte herE alloWs one to pin dowN the pure seTS OF the theoRy up TO fULl isomorphism; sOmethIng which is NOt possibLe in $ZfC^2$.
The refErence for THE McGee is The FolLowIng:
vANn, mcGee-How We LeaRN mathEmAtical LAngUage, The phiLosOphIcaL REview, Vol. 106, NO. 1 (Jan., 1997), pp. 35-68
As FoR tHe ReLatIonshIP between InDivIdUalS and cLAsses; I Don't sEe a lInK cLEarLy myselF. hoWEVer, tHe FoLlowIng Is A papeR in wHIch You mighT be intereSteD, In whIcH CHristopHer Menzel arguEs That ordinaLs ShoUld be tHOUght of as Urelemente and considers a SEt theorY of Sorts WherE the ordinAls Exist iN $V_0$ aND form a Set at $V_1$. in thiS cAse WE Have wHAT wE'd nOrMally think OF As a PropeR cLass (The ordiNals) forming a set on tHE baSis of a specifiC viEw abOUT tHe nATuRE of UrELemENTe. The reference fOr that papeR iS:
meNzel, ChristOPheR (1986). ON the iteRative eXplanATion of tHe paradoxEs. PhilosoPhIcal sTUdiEs 49 (1):37 - 61

 Q:

ExceptiOn: EXC_BAD_iNSTRUCTIon (
 is unsurprising that in t he last 40  year s i ndi vi dual s
 have largely d i sapp eared from view.

Forfurth er rela t ed  disc ussions ab o u t b as ic  is su e s,  seePot ter's i mmensely h elp fu l book. @Nei l Ba rton thengiv es some exce lle nt fur th ers ugges tio ns fo r intr i guingglimpsesbe y ond.
A :

So i n d iv idua ls (or "urelement e "a s they are som etimes  c a ll e d ) a reused veryli ttlei n moder n  m a t h ema t ics. This ispartly beca u sethe se tthe o retichiera rc h y i s very big;  wecan repre sent m o st math e maticsin the  fi rst  few in fi nit el eve l s,  so the  ureleme nt eare s impl y a n  unn ece ssar y com plication. 
H owe ver, set  theo ry wi th u re lemen te has  been  p ut to interesti ng * meta*math ema ti cal  u se. F o r inst anc e,Vann Mc Gee has sho wn t h at  (given unrestrict ed f ir st order  quant i fi ca t ion) one  c anprov e thatthep ur e sets i n anym od el  of sec on d-orde r$ZF CU$  ($ZF C U$ i s stan dard sec ond-o r der $ZFC^2$ wi t h two further ax i o ms adde d;that thereis a t  lea st o n eure l ement  andth a tt he urelemente formaset) a re is omorphic. Thi s contrast s w ith thecorr e sp o nding result f or $Z FC^2$ that given an y two  modelsof $ZFC^2 $ either t hetwo  ar e i s o mo rphic or onei s  iso mo rphic t o a  proper  in iti alseg me nt of the  other.Th us  t he  ad ditio n  of urel em ent eher e all o ws one  to p in d ow nt hepure se t so f  the  t he oryupto  full  iso m orp hism; s omethingwhi c h is  n ot  possib le in $ZFC^2$ .The refere nc e f or the M cGee isthe following:
Vann, Mc G ee-HowWeLearn  Mat hematical  La nguage , T h e Phil osophi cal R ev iew , Vol.1 0 6,  No .1 (Jan., 1 9 9 7),  pp.35 -68As forthe relationship b e twe en individual s a nd c l a ss es; Id on' ts eea link clearly my self. Howe ve r ,the follow i ngis  a pape r in wh ich y o u might  be inter ested, in  w hich C hri stopher Me nzel arg ues thato rdina l sshoul d b e thou gh t o f asurelem e nte  andconsid er s a se t the or y of sor ts where the ordinals e xist i n $V_ 0$and forma s e t a t $V_1$.In t his case w e h ave  what  we ' d nor mall y  t hin k  of a s ap roper cla s s(th e or dinals) for m i n g a  setont he bas is o f a specific view about the natu re o f ure lem e nte.  T he reference f orth a t  paper i s: 
Menzel, Ch ristophe r( 1986) . On t he ite rativee x pl a nation  ofthe  paradoxe s.Ph i losophi ca lS tudies  49(1 ):37 -  61

Q :

E x c eption: EXC_BAD_ INSTR U C TION( 
 is_unsurprising that_in the last 40_years individuals
__have largely_disappeared_from view.

For further_related discussions about_basic issues, see Potter's_immensely helpful book._@NeilBarton_then gives some excellent further suggestions for intriguing glimpses beyond.

A:

So individuals (or "urelemente" as_they_are sometimes_called)_are_used very little in modern_mathematics. This is partly because_the set_theoretic hierarchy is very big; we can represent_most_mathematics in the_first few infinite levels, so the urelemente are simply_an unnecessary complication. 
However, set theory_with urelemente has_been_put_to interesting *meta*mathematical use._For instance, Vann McGee has shown_that (given unrestricted first order quantification)_one can prove that the pure sets_in any model of second-order $ZFCU$_($ZFCU$ is standard second-order $ZFC^2$_with two_further axioms added; that there_is at least_one urelement_and that the_urelemente form a set) are isomorphic._This contrasts with_the corresponding result for $ZFC^2$ that_given_any two models_of_$ZFC^2$_either the_two are isomorphic_or_one is_isomorphic_to a proper initial segment of_the_other. Thus the addition of urelemente here_allows one to pin_down_the pure sets of_the theory up to full_isomorphism; something which is not possible_in $ZFC^2$.
The_reference for_the McGee is the following:
Vann, McGee-How We Learn Mathematical Language, The_Philosophical Review, Vol. 106, No. 1_(Jan., 1997), pp. 35-68
As_for the_relationship_between individuals and_classes;_I don't_see a link clearly myself. However, the_following is_a paper in which you might_be interested, in which_Christopher_Menzel argues that ordinals should be_thought of as urelemente and considers_a set theory of sorts_where_the_ordinals exist in $V_0$ and_form a set at $V_1$. In_this case we_have what we'd normally think of as_a_proper class (the ordinals) forming a_set_on the basis of a specific_view_about_the nature of urelemente. The_reference for that paper is:
Menzel, Christopher_(1986). On the iterative explanation of the paradoxes. Philosophical_Studies 49 (1):37_- 61

 Q:

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