. _Tres partes_: cf. I. 19. _Et a vobismet_: "and especially by you".
The threefold division was peculiarly Stoic, though used by other schools,
cf. Sext. _P.H._ II. 13 (on the same subject) [Greek: hoi Stoikoi kai alloi
tines]. For other modes of dividing philosophy see Sext. _A.M._ VII. 2. _At
illud ante_: this is my em. for the MSS. _velut illud ante_, which probably
arose from a marginal variant "_vel ut_" taking the place of _at_; cf. a
similar break in 40 _sed prius_, also in 128 _at paulum ante_. Such breaks
often occur in Cic., as in _Orator_ 87 _sed nunc aliud_, also _T.D._ IV. 47
_repenam fortasse, sed illud ante._ For _velut_ Halm writes _vel_ (which
Bait. takes), Dav. _verum_. _Inflatus tumore_: cf. _De Off._ I. 91 _inflati
opinionibus._ Bentl. read _errore_. _Cogere_: this word like [Greek:
anankazein] and [Greek: biazesthai] often means simply to argue
irresistibly. _Initia_: as in 118, bases of proof, themselves naturally
incapable of proof, so [Greek: archai] in Gk. _Digitum_: cf. 58, 143.
_Punctum esse_ etc.: [Greek: semeion estin ou meros outhen] (Sext. _P.H._
III. 39), [Greek: stigme] = [Greek: to ameres] (_A.M._ IX. 283, 377).
_Extremitatem_: = [Greek: epiphaneian]. _Libramentum_: so this word is used
by Pliny (see Forc.) for the slope of a hill. _Nulla crassitudo_: in Sext.
the [Greek: epiphaneia] is usually described not negatively as here, but
positively as [Greek: mekos meta platous] (_P.H._ III. 39), [Greek: peras]
(_extremitas_) [Greek: somatos duo echon diastaseis, mekos kai platos]
(_A.M._ III. 77). _Liniamentum ... carentem_: a difficult passage. Note (1)
that the line is defined in Greek as [Greek: mekos aplates]. (Sext. as
above), (2) that Cic. has by preference described the point and surface
negatively. This latter fact seems to me strong against the introduction of
_longitudinem_ which Ursinus, Dav., Orelli, Baiter and others propose by
conjecture. If anything is to be introduced, I would rather add _et
crassitudine_ before _carentem_, comparing I. 27 _sine ulla specie et
carentem omni illa qualitate_. I have merely bracketed _carentem_, though I
feel Halm's remark that a verb is wanted in this clause as in the other
two, he suggests _quod sit sine_. Hermann takes _esse_ after _punctum_ as
strongly predicative ("there _is_ a point," etc.), then adds _similiter_
after _liniamentum_ and ejects _sine ulla_. Observe the awkwardness of
having the _line_ treated of after the _superficies_, which