rtall, intellectual, simple and indiuisible: and thynges naturall,
mortall, sensible, compounded and diuisible. Probabilitie and sensible
prose, may well serue in thinges naturall: and is commendable: In
Mathematicall reasoninges, a probable Argument, is nothyng regarded: nor
yet the testimony of sense, any whit credited: But onely a perfect
demonstration, of truthes certaine, necessary, and inuincible:
vniuersally and necessaryly concluded: is allowed as sufficient for "an
Argument exactly and purely Mathematical."

[Note the worde, Vnit, to expresse the Greke Monas,
& not Vnitie: as we haue all, commonly, till now, vsed.]

Of _Mathematicall_ thinges, are two principall kindes: namely, _Number_,
and _Magnitude_.

[Number.]

_Number_, we define, to be, a certayne Mathematicall Summe, of _Vnits_.
And, an _Vnit_, is that thing Mathematicall, Indiuisible, by
participation of some likenes of whose property, any thing, which is in
deede, or is counted One, may resonably be called One. We account an
_Vnit_, a thing _Mathematicall_, though it be no Number, and also
indiuisible: because, of it, materially, Number doth consist: which,
principally, is a thing _Mathematicall_.

[Magnitude.]

_Magnitude_ is a thing _Mathematicall_, by participation of some likenes
of whose nature, any thing is iudged long, broade, or thicke. "A thicke
_Magnitude_ we call a _Solide_, or a _Body_. What _Magnitude_ so euer,
is Solide or Thicke, is also broade, & long. A broade magnitude, we call
a _Superficies_ or a Plaine. Euery playne magnitude, hath also length.
A long magnitude, we terme a _Line_. A _Line_ is neither thicke nor
broade, but onely long: Euery certayne Line, hath two endes:

[A point.]

The endes of a line, are _Pointes_ called. A _Point_, is a thing
_Mathematicall_, indiuisible, which may haue a certayne determined
situation." If a Poynt moue from a determined situation, the way wherein
it moued, is also a _Line_: mathematically produced, whereupon, of the
auncient Mathematiciens,

[A Line.]

a _Line_ is called the race or course of a _Point_. A Poynt we define,
by the name of a thing Mathematicall: though it be no Magnitude, and
indiuisible: because it is the propre ende, and bound of a Line: which
is a true _Magnitude_.

[Magnitude.]

And _Magnitude_ we may define to be that thing _Mathematicall_, which is
diuisible for euer, in partes diuisible, long, broade or thicke.
Therefore thou