the connection of my reasonings; but that he must not then give it
up in despair, although he may not everywhere sufficiently discover
the connection of the proof, or understand all the reasonings--it
being only necessary to mark with a pen the places where the
difficulties occur, and continue to read without interruption to the
end; then, if he does not grudge to take up the book a third time, I
am confident he will find in a fresh perusal the solution of most of
the difficulties he will have marked before; and that, if any still
remain, their solution will in the end be found in another reading.

I have observed, on examining the natural constitutions of different
minds, that there are hardly any so dull or slow of understanding as
to be incapable of apprehending good opinions, or even of acquiring
all the highest sciences, if they be but conducted along the right
road. And this can also be proved by reason; for, as the principles
are clear, and as nothing ought to be deduced from them, unless most
manifest inferences, no one is so devoid of intelligence as to be
unable to comprehend the conclusions that flow from them. But,
besides the entanglement of prejudices, from which no one is
entirely exempt, although it is they who have been the most ardent
students of the false sciences that receive the greatest detriment
from them, it happens very generally that people of ordinary
capacity neglect to study from a conviction that they want ability,
and that others, who are more ardent, press on too rapidly: whence
it comes to pass that they frequently admit principles far from
evident, and draw doubtful inferences from them. For this reason, I
should wish to assure those who are too distrustful of their own
ability that there is nothing in my writings which they may not
entirely understand, if they only take the trouble to examine them;
and I should wish, at the same time, to warn those of an opposite