1. Though after what I have acknowledged, _Pyrophilus_, of the Abstruse
Nature of Colours in _particular_, you will easily believe, that I pretend
not to give you a Satisfactory account of Whiteness and Blackness; Yet not
wholly to frustrate your Expectation of my offering something by way of
Specimen towards the Explication of some Colours in particular, I shall
make choice of These as the most Simple Ones, (and by reason of their
mutual Opposition the Least hardly explicable) about which to present you
my Thoughts, upon condition you will take them at most to be my
Conjectures, not my Opinions.

2. When I apply'd my Self to consider, how the cause of Whiteness might be
explan'd by Intelligible and Mechanical Principles, I remembred not to have
met with any thing among the Antient _Corpuscularian_ Philosophers,
touching the Quality we call Whiteness, save that _Democritus_ is by
_Aristotle_ said to have ascrib'd the Whiteness of Bodies to their
Smoothness, and on the contrary their Blackness to their Asperity.[6] But
though about the Latter of those Qualities his Opinion be allowable, as we
shall see anon, yet that he heeds a Favourable Interpretation in what is
Deliver'd concerning the First, (at least if his Doctrine be not
Mis-represented in this point, as it has been in many others) we shall
quickly have Occasion to manifest. But amongst the _Moderns_, the most
Learned _Gassendus_ in his Ingenious Epistle publish'd in the Year 1642.
_De apparente Magnitudine solis humilis & sublimis_, reviving the
_Atomical_ Philosophy, has, though but Incidentally, deliver'd something
towards the Explication of Whiteness upon Mechanical Principles: And
because no Man that I know of, has done so before him, I shall, to be sure
to do him Right, give you his Sense in his own Words:[7] _Cogites velim_
(says he) _lucem quidem in Diaphano nullius coloris videri, sed in Opaco
tamen terminante Candicare, ac tantò magis, quantò densior seu collectior