require, and which it is impossible for me to make without the assistance
of others:  and, without flattering myself so much as to expect the public
to take a large share in my interests, I am yet unwilling to be found so
far wanting in the duty I owe to myself, as to give occasion to those who
shall survive me to make it matter of reproach against me some day, that I
might have left them many things in a much more perfect state than I have
done, had I not too much neglected to make them aware of the ways in which
they could have promoted the accomplishment of my designs.

And I thought that it was easy for me to select some matters which should
neither be obnoxious to much controversy, nor should compel me to expound
more of my principles than I desired, and which should yet be sufficient
clearly to exhibit what I can or cannot accomplish in the sciences.
Whether or not I have succeeded in this it is not for me to say; and I do
not wish to forestall the judgments of others by speaking myself of my
writings; but it will gratify me if they be examined, and, to afford the
greater inducement to this I request all who may have any objections to
make to them, to take the trouble of forwarding these to my publisher, who
will give me notice of them, that I may endeavor to subjoin at the same
time my reply; and in this way readers seeing both at once will more easily
determine where the truth lies; for I do not engage in any case to make
prolix replies, but only with perfect frankness to avow my errors if I am
convinced of them, or if I cannot perceive them, simply to state what I
think is required for defense of the matters I have written, adding
thereto no explication of any new matte that it may not be necessary to
pass without end from one thing to another.

If some of the matters of which I have spoken in the beginning of the
"Dioptrics" and "Meteorics" should offend at first sight, because I call
them hypotheses and seem indifferent about giving proof of them, I request
a patient and attentive reading of the whole, from which I hope those
hesitating will derive satisfaction; for it appears to me that the
reasonings are so mutually connected in these treatises, that, as the last
are demonstrated by the first which are their causes, the first are in
their turn demonstrated by the last which are their effects.  Nor must it
be imagined that I here commit the fallacy which the logicians call a
circle; for since experience renders the majority of these effects most
certain, the causes from which I deduce them do not serve so much to
establish their reality as to explain their existence; but on the
contrary, the reality of the causes is established by the reality of the
effects.  Nor have I called them hypotheses with any other end in view
except that it may be known that I think I am able to deduce them from
those first truths which I have already expounded; and yet that I have
expressly determined not to do so, to prevent a certain class of minds
from thence taking occasion to build some extravagant philosophy upon what
they may take to be my principles, and my being blamed for it.  I refer to
those who imagine that they can master in a day all that another has taken
twenty years to think out, as soon as he has spoken two or three words to
them on the subject; or who are the more liable to error and the less
capable of perceiving truth in very proportion as they are more subtle and
lively.  As to the opinions which are truly and wholly mine, I offer no
apology for them as new, -- persuaded as I am that if their reasons be
well considered they will be found to be so simple and so conformed, to
common sense as to appear less extraordinary and less paradoxical than any
others which can be held on the same subjects; nor do I even boast of being
the earliest discoverer of any of them, but only of having adopted them,
neither because they had nor because they had not been held by others,
but solely because reason has convinced me of their truth.

Though artisans may not be able at once to execute the invention which is
explained in the "Dioptrics," I do not think that any one on that account
is entitled to condemn it; for since address and practice are required in
order so to make and adjust the machines described by me as not to
overlook the smallest particular, I should not be less astonished if they
succeeded on the first attempt than if a person were in one day to become
an accomplished performer on the guitar, by merely having excellent sheets
of music set up before him.  And if I write in French, which is the
language of my country, in preference to Latin, which is that of my
preceptors, it is because I expect that those who make use of their
unprejudiced natural reason will be better judges of my opinions than
those who give heed to the writings of the ancients only; and as for those
who unite good sense with habits of study, whom alone I desire for judges,
they will not, I feel assured, be so partial to Latin as to refuse to
listen to my reasonings merely because I expound them in the vulgar tongue.

In conclusion, I am unwilling here to say anything very specific of the
progress which I expect to make for the future in the sciences, or to bind
myself to the public by any promise which I am not certain of being able
to fulfill; but this only will I say, that I have resolved to devote what
time I may still have to live to no other occupation than that of
endeavoring to acquire some knowledge of Nature, which shall be of such a
kind as to enable us therefrom to deduce rules in medicine of greater
certainty than those at present in use; and that my inclination is so much
opposed to all other pursuits, especially to such as cannot be useful to
some without being hurtful to others, that if, by any circumstances, I had
been constrained to engage in such, I do not believe that I should have
been able to succeed.  Of this I here make a public declaration, though well
aware that it cannot serve to procure for me any consideration in the
world, which, however, I do not in the least affect; and I shall always
hold myself more obliged to those through whose favor I am permitted to
enjoy my retirement without interruption than to any who might offer me
the highest earthly preferments.

END.
.