Principles of Philosophy

"CCIV. [T]hings which our senses do not perceive... it is sufficient to explain how they can be (and... this is all... Aristotle has essayed)."

"III. In what sense... all things were created for the sake of man."

"CXCIII. Of smell. [N]erves ...appendages of the brain ...are moved by the particles of terrestrial bodies, separated and flying in the air ...From the different motions of these particles arise the sensations of the different smells."

"CCV. [T]here is a moral certainty that all the things of this world are such as has been here shown they may be. ...I ...distinguish two kinds of certitude. ...[F]irst is ...moral ...[i.e.,] a certainty sufficient for the conduct of life, though, if we look to ...God, what is morally certain may be false. ...[T]hey who observe how many things regarding the magnet, fire, and the fabric of the whole world, are here deduced from a very small number of principles, though they deemed ...I had taken them up at random and without grounds, will ...acknowledge that it could hardly happen that so many things should cohere if these principles were false."

"[W]hen the blood is so thick that it flows ...sparingly into the ventricles of the heart ...not ...sufficiently dilated, it excites in the same nerves a motion ...which, communicated to the brain, gives to the mind the sensation of sadness ...And all the other causes which move these nerves in the same way may also give ...the same sensation. ...[O]ther movements of the same nerves produce other effects, as ...love, hate, fear, anger, etc... [A]s far as they are confused thoughts which the mind has not from itself ...but from ...the body ...[T]here is the widest difference between these passions and the distinct thoughts which we have of what ought to be loved, or chosen, or shunned, etc."

"By a body as a part of matter, I understand all that which is transferred together, although... perhaps composed of... parts, which in themselves have other motions; and... it is the transporting and not the force or action which transports... motion is always in the movable thing... [I]t is a mode of the movable thing, and not a substance, just as figure is a property of the thing figured, and repose of that which is at rest."

"I have ...described this earth, and ...the whole visible world, as if ...a machine in which there was nothing ...consider except ...figures and motions of its parts, whereas our senses present ...many other things ...[e.g.,] colors, smells, sounds ...[etc.,] of which, if I did not speak ...it would be thought I ... omitted ...the majority of ...nature."

"CXCII. Of taste. ...[N]erves scattered over the tongue and ...parts ...are diversely moved by the particles ...and ...cause sensations ...according to the diversity of figure in these particles."

"CC. [T]his treatise contains no principles which are not universally received; and... this philosophy is not new, but... the most ancient and common."

"CCVII. [H]owever, I submit all my opinions to the authority of the church. ... I affirm nothing, but submit all these my opinions to the authority [and judgment] of the church... I desire no one to believe anything I may have said, unless he is constrained to admit it by the force and evidence of reason."

"CXCVIII. [B]y our senses we know nothing of external objects beyond their figure [or situation], magnitude, and motion."

"CXCIV. Of hearing. ...[N]erves within the ears, so attached to three small bones ...the first ...rests on the small membrane ...the tympanum ...[D]iverse vibrations which the surrounding air communicates to this membrane, are transmitted to the mind by these nerves, and those vibrations give rise ...to the sensations of the different sounds."

"CLXXXIX. [P]erception (sensus)... and how we perceive."

"I. [W]e cannot think too highly of the works of God."

"II. [W]e ought to beware lest, in our presumption, we imagine that the ends which God proposed to himself in the creation of the world are understood by us."

"[B]ecause I have not ...acquired sufficient knowledge of all the matters ...to treat in these two last parts, and do not know whether I ever shall ...finish them, I ...here subjoin a few things regarding the objects of our senses."

"CXC. Distinction of the senses; and... of the internal... [i.e.,] affections of the mind (passions), and the natural appetites. ...We can distinguish ...seven principal classes of nerves, ...two belong to the internal, and ...five to the external senses. ...[N]rves ... to the stomach ...oesophagus ...fauces, and the other internal parts ...subservient to ...natural wants, constitute ...the natural appetite (appetitus naturalis) The other internal sense ...embraces all the emotions (commotiones) of the mind or passions, and affections, as joy, sadness, love, hate... [etc.] depends upon ...nerves ...to the heart ..."

"CXCI. Of the external senses... first of touch."

"CXCVI. [T]he soul perceives only in so far as it is in the brain. ...[T]he soul does not perceive in so far as it is in each [body] member ...but only in so far as it is in the brain, where the nerves ...convey to it ...actions of ...external objects ...[T]here are various maladies, which ...affect the brain alone, yet bring disorder upon, or deprive ...use of, our senses ..."

"CXCIX. [T]here is no phenomenon of nature whose explanation has been omitted in this treatise."

"CCIII. [W]e may arrive at the knowledge of the figures (magnitude), and motions of the insensible particles of bodies. ...[S]ince I assign determinate figures, magnitudes, and motions to the insensible particles... how... have [I] come by my knowledge of them. ...I ...considered in general all the clear and distinct notions of material things ...in our understanding, and that, finding no others except ...figures, magnitudes, and motions, and ...rules according to which these three ...can be diversified by each other, which rules are ...of geometry and mechanics ...I judged that all the knowledge ...of nature must ...be drawn from this ...I considered the chief differences ...between the magnitudes, and figures, and situations of bodies insensible ... and what sensible effects could be produced by their ...modes of ...contact ...[W]hen I found like effects in the bodies that we perceive ...I judged ...they could have been thus produced ...[A]ll the rules of mechanics belong also to physics, of which it is a part ...for it is not less natural for a clock ...to mark the hours, than for a tree ...to produce ...fruit ...[S]o from considering the sensible effects and parts of natural bodies, I have essayed to determine the character of their causes and insensible parts."

"CCVI. [W]e possess even more than a moral certainty of it."

"CCII. [T]he philosophy of Democritus is not less different from ours than from the common. ...[I]t may be said that Democritus ...supposed ...corpuscles ...of various figures, sizes, and motions, from the heaping together and mutual concourse of which all sensible bodies arose; and, nevertheless, his mode of philosophizing is commonly rejected by all. ...I reply that the philosophy of Democritus was ...rejected ...because he supposed ...corpuscles ...indivisible, on which ground I also reject it ...second ...because he imagined ...a vacuum about them, which I show to be impossible; thirdly, because he attributed gravity to these bodies, of which I deny ...in so far as a body is considered by itself, because it is a quality that depends on the relations of situation and motion which several bodies bear to each other; and, finally, because he has not explained ...how all things arose from the concourse of corpuscles alone, or, if he gave this explanation with regard to a few of them, his whole reasoning was far from being coherent (or such as would warrant ...extending the same explanation to the whole of nature)."

"CCI. [S]ensible bodies are composed of insensible particles. ...I allow many particles in each body... perceived by none of our senses... [W]ho ever observed by the senses those small bodies that are in one day added to a tree while growing? ...[I]n ...division ...parts may become so small as to be ...imperceptible."

"CXCVII. [T]he nature of the mind is such that from the motion alone of the body various sensations can be excited in it."

"CXCV. Of sight. ...[E]xtremities of the optic nerves, composing the ...retina, are ...moved ...only by the globules of the second element, whence we have the sense of light and colors: as I ...explained in the Dioptrics and treatise of Meteors."

"[B]lood ...pure and well tempered ...dilates in the heart more readily and strongly ...so enlarges and moves the small nerves scattered around the orifices ...thence a corresponding movement in the brain ...affects the mind with a ...feeling of joy; and ...these ..nerves ... moved in the same way ...by other causes ...excite ...the same feeling (sensus, sentiment)."

"[M]ovements... excited in the brain by the nerves... affect the soul or mind, which is intimately conjoined with the brain, according to the diversity of the motions... [T]he diverse affections of the mind or thoughts that... arise from these motions, are... perceptions of the senses (sensuum perceptiones), or... commonly... sensations (sensus)."

"CLXXXVIII. [W]hat is to be borrowed from disquisitions on animals and man to advance the knowledge of material objects."

"[T]he principles are clear, and... no one is so devoid of intelligence as to be unable to comprehend the conclusions that flow from them."

"[T]here 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... conducted along the right road."

"The same may be said of a vacuum and atoms, of heat and cold, of dryness and humidity, and of salt, sulphur, and mercury, and the other things... some... adopted as... principles."

"[T]hose imbued with my doctrines have much less difficulty in comprehending the writings of others, and estimating their true value... and this is... the opposite of... such as commenced with the ancient philosophy, namely, that the more they have studied it the less fit are they for rightly apprehending the truth."

"[T]hough I have not treated in it of all matters—that being impossible—I think I have so explained... that they who read... attentively will have ground... that it is unnecessary to seek for any other principles... to arrive at the most exalted knowledge of which the mind of man is capable..."

"[T]he philosophers... all laid down as a principle what they did not perfectly know. ...I know none of them who did not suppose that there was gravity in terrestrial bodies; but although experience shows us... [heavy] bodies... descend towards the centre of the earth, we do not... know the nature of gravity... [i.e.,] the cause or principle in virtue of which bodies descend, and we must derive our knowledge of it from some other source."

"[T]hey who make pretensions to philosophy are often less wise and reasonable than others who never applied themselves..."

"But... there has been no one up to the present, who... has adopted them as principles of philosophy... [i.e.,] as such that we can deduce from them the knowledge of whatever else is in the world."

"The second circumstance that proves the clearness of these principles is, that they have been known in all ages, and even received as true and indubitable by all men, with the exception only of the existence of God, which has been doubted by some, because they attributed too much to the perceptions of the senses, and God can neither be seen nor touched."

"From ignorance of this truth, or... from neglect of it, the majority of those who... aspired to be philosophers, blindly followed Aristotle, so... frequently corrupted... his writings, and attributed... opinions... he would not recognise... and those who did not follow him, among whom are... many of the greatest minds, did yet not escape... his opinions in their youth... the staple... in the schools; and thus... they could not rise to the knowledge of true principles."

"Such are in sum the principles from which I deduce all other truths."

"Those are all the principles of which I avail myself touching immaterial or metaphysical objects, from which I most clearly deduce these other principles of physical or corporeal things, namely, that there are bodies extended in length, breadth, and depth, which are of diverse figures and are moved in a variety of ways."

"[W]hile we only possess... knowledge... acquired in the... four grades of wisdom, we ought not to doubt... things that appear... true in... the conduct of life, nor esteem them as so certain that we cannot change our opinions.., even though constrained by... reason."

"The greatest favourites of fortune—those who have health, honours, and riches in abundance—are not more exempt from [these] aspirations... nay... [T]hese are the persons who sigh... most deeply after another good greater and more perfect... But the supreme good, considered by natural reason without the light of faith, is... knowledge of truth through its first causes... [i.e.,] the wisdom of which philosophy is the study. ...[A]ll that is required to gain assent to their truth is that they be well stated."

"[T]o live without philosophising is... the same as keeping the eyes closed..."

"XII. [E]veryone does not come equally to know this."

"XI. [W]e can know our mind more clearly than our body."

"XIII. [[Knowledge|[K]nowledge]] of other things depends upon the knowledge of God."

"XIV. [W]e may validly infer the existence of God from necessary existence being comprised in the concept we have of him."

"XV. [N]ecessary existence is not in the same way comprised in the notions which we have of other things, but merely contingent existence."

"I have taken... for the first principle, from which I... deduced the following truths... that there is a God who is the author of all... and... being the source of all truth, cannot have created our understanding... as to be deceived in... judgments... of the things of which it possesses... clear and distinct perception."