what these truths are, that the more judicious may be able to determine
whether a more special account of them would conduce to the public
advantage. I have ever remained firm in my original resolution to suppose
no other principle than that of which I have recently availed myself in
demonstrating the existence of God and of the soul, and to accept as true
nothing that did not appear to me more clear and certain than the
demonstrations of the geometers had formerly appeared; and yet I venture
to state that not only have I found means to satisfy myself in a short
time on all the principal difficulties which are usually treated of in
philosophy, but I have also observed certain laws established in nature by
God in such a manner, and of which he has impressed on our minds such
notions, that after we have reflected sufficiently upon these, we cannot
doubt that they are accurately observed in all that exists or takes place
in the world and farther, by considering the concatenation of these laws,
it appears to me that I have discovered many truths more useful and more
important than all I had before learned, or even had expected to learn.

But because I have essayed to expound the chief of these discoveries in a
treatise which certain considerations prevent me from publishing, I cannot
make the results known more conveniently than by here giving a summary of
the contents of this treatise. It was my design to comprise in it all
that, before I set myself to write it, I thought I knew of the nature of
material objects. But like the painters who, finding themselves unable to
represent equally well on a plain surface all the different faces of a
solid body, select one of the chief, on which alone they make the light
fall, and throwing the rest into the shade, allow them to appear only in
so far as they can be seen while looking at the principal one; so, fearing
lest I should not be able to compense in my discourse all that was in my
mind, I resolved to expound singly, though at considerable length, my
opinions regarding light; then to take the opportunity of adding something