But since that time other reasons have occurred to me,by which I have been led to change my opinion,and to think that I ought indeed to go on committing to writing all the results which I deemed of any moment,as soon as I should have tested their truth,and to bestow the same care upon them as I would have done had it been my design to publish them.This course commended itself to me,as well because I thus afforded myself more ample inducement to examine them thoroughly,for doubtless that is always more narrowly scrutinized which we believe will be read by many,than that which is written merely for our private use (and frequently what has seemed to me true when I first conceived it,has appeared false when Ihave set about committing it to writing),as because I thus lost no opportunity of advancing the interests of the public,as far as in me lay,and since thus likewise,if my writings possess any value,those into whose hands they may fall after my death may be able to put them to what use they deem proper.But I resolved by no means to consent to their publication during my lifetime,lest either the oppositions or the controversies to which they might give rise,or even the reputation,such as it might be,which they would acquire for me,should be any occasion of my losing the time that I had set apart for my own improvement.For though it be true that every one is bound to promote to the extent of his ability the good of others,and that to be useful to no one is really to be worthless,yet it is likewise true that our cares ought to extend beyond the present,and it is good to omit doing what might perhaps bring some profit to the living,when we have in view the accomplishment of other ends that will be of much greater advantage to posterity.And in truth,Iam quite willing it should be known that the little I have hitherto learned is almost nothing in comparison with that of which I am ignorant,and to the knowledge of which I do not despair of being able to attain;for it is much the same with those who gradually discover truth in the sciences,as with those who when growing rich find less difficulty in making great acquisitions,than they formerly experienced when poor in making acquisitions of much smaller amount.Or they may be compared to the commanders of armies,whose forces usually increase in proportion to their victories,and who need greater prudence to keep together the residue of their troops after a defeat than after a victory to take towns and provinces.For he truly engages in battle who endeavors to surmount all the difficulties and errors which prevent him from reaching the knowledge of truth,and he is overcome in fight who admits a false opinion touching a matter of any generality and importance,and he requires thereafter much more skill to recover his former position than to make great advances when once in possession of thoroughly ascertained principles.As for myself,if I have succeeded in discovering any truths in the sciences (and I trust that what is contained in this volume 1will show that I have found some),I can declare that they are but the consequences and results of five or six principal difficulties which I have surmounted,and my encounters with which I reckoned as battles in which victory declared for me.I will not hesitate even to avow my belief that nothing further is wanting to enable me fully to realize my designs than to gain two or three similar victories;and that I am not so far advanced in years but that,according to the ordinary course of nature,I may still have sufficient leisure for this end.But I conceive myself the more bound to husband the time that remains the greater my expectation of being able to employ it aright,and I should doubtless have much to rob me of it,were I to publish the principles of my physics:for although they are almost all so evident that to assent to them no more is needed than simply to understand them,and although there is not one of them of which I do not expect to be able to give demonstration,yet,as it is impossible that they can be in accordance with all the diverse opinions of others,I foresee that Ishould frequently be turned aside from my grand design,on occasion of the opposition which they would be sure to awaken.
It may be said,that these oppositions would be useful both in making me aware of my errors,and,if my speculations contain anything of value,in bringing others to a fuller understanding of it;and still farther,as many can see better than one,in leading others who are now beginning to avail themselves of my principles,to assist me in turn with their discoveries.But though I recognize my extreme liability to error,and scarce ever trust to the first thoughts which occur to me,yet-the experience I have had of possible objections to my views prevents me from anticipating any profit from them.For I have already had frequent proof of the judgments,as well of those I esteemed friends,as of some others to whom I thought I was an object of indifference,and even of some whose malignancy and envy would,I knew,determine them to endeavor to discover what partiality concealed from the eyes of my friends.But it has rarely happened that anything has been objected to me which I had myself altogether overlooked,unless it were something far removed from the subject:so that I have never met with a single critic of my opinions who did not appear to me either less rigorous or less equitable than myself.
And further,I have never observed that any truth before unknown has been brought to light by the disputations that are practised in the schools;for while each strives for the victory,each is much more occupied in making the best of mere verisimilitude,than in weighing the reasons on both sides of the question;and those who have been long good advocates are not afterwards on that account the better judges.
