Three years have now elapsed since I finished the treatise containing all these matters;and I was beginning to revise it,with the view to put it into the hands of a printer,when I learned that persons to whom I greatly defer,and whose authority over my actions is hardly less influential than is my own reason over my thoughts,had condemned a certain doctrine in physics,published a short time previously by another individual to which I will not say that I adhered,but only that,previously to their censure I had observed in it nothing which I could imagine to be prejudicial either to religion or to the state,and nothing therefore which would have prevented me from giving expression to it in writing,if reason had persuaded me of its truth;and this led me to fear lest among my own doctrines likewise some one might be found in which I had departed from the truth,notwithstanding the great care I have always taken not to accord belief to new opinions of which I had not the most certain demonstrations,and not to give expression to aught that might tend to the hurt of any one.This has been sufficient to make me alter my purpose of publishing them;for although the reasons by which I had been induced to take this resolution were very strong,yet my inclination,which has always been hostile to writing books,enabled me immediately to discover other considerations sufficient to excuse me for not undertaking the task.
And these reasons,on one side and the other,are such,that not only is it in some measure my interest here to state them,but that of the public,perhaps,to know them.
I have never made much account of what has proceeded from my own mind;and so long as I gathered no other advantage from the method I employ beyond satisfying myself on some difficulties belonging to the speculative sciences,or endeavoring to regulate my actions according to the principles it taught me,I never thought myself bound to publish anything respecting it.For in what regards manners,every one is so full of his own wisdom,that there might be found as many reformers as heads,if any were allowed to take upon themselves the task of mending them,except those whom God has constituted the supreme rulers of his people or to whom he has given sufficient grace and zeal to be prophets;and although my speculations greatly pleased myself,I believed that others had theirs,which perhaps pleased them still more.But as soon as I had acquired some general notions respecting physics,and beginning to make trial of them in various particular difficulties,had observed how far they can carry us,and how much they differ from the principles that have been employed up to the present time,I believed that I could not keep them concealed without sinning grievously against the law by which we are bound to promote,as far as in us lies,the general good of mankind.For by them I perceived it to be possible to arrive at knowledge highly useful in life;and in room of the speculative philosophy usually taught in the schools,to discover a practical,by means of which,knowing the force and action of fire,water,air the stars,the heavens,and all the other bodies that surround us,as distinctly as we know the various crafts of our artisans,we might also apply them in the same way to all the uses to which they are adapted,and thus render ourselves the lords and possessors of nature.And this is a result to be desired,not only in order to the invention of an infinity of arts,by which we might be enabled to enjoy without any trouble the fruits of the earth,and all its comforts,but also and especially for the preservation of health,which is without doubt,of all the blessings of this life,the first and fundamental one;for the mind is so intimately dependent upon the condition and relation of the organs of the body,that if any means can ever be found to render men wiser and more ingenious than hitherto,I believe that it is in medicine they must be sought for.It is true that the science of medicine,as it now exists,contains few things whose utility is very remarkable:but without any wish to depreciate it,Iam confident that there is no one,even among those whose profession it is,who does not admit that all at present known in it is almost nothing in comparison of what remains to be discovered;and that we could free ourselves from an infinity of maladies of body as well as of mind,and perhaps also even from the debility of age,if we had sufficiently ample knowledge of their causes,and of all the remedies provided for us by nature.But since I designed to employ my whole life in the search after so necessary a science,and since I had fallen in with a path which seems to me such,that if any one follow it he must inevitably reach the end desired,unless he be hindered either by the shortness of life or the want of experiments,I judged that there could be no more effectual provision against these two impediments than if I were faithfully to communicate to the public all the little I might myself have found,and incite men of superior genius to strive to proceed farther,by contributing,each according to his inclination and ability,to the experiments which it would be necessary to make,and also by informing the public of all they might discover,so that,by the last beginning where those before them had left off,and thus connecting the lives and labours of many,we might collectively proceed much farther than each by himself could do.
