Preface
Most writers on the emotions and on human conduct seem to be treating rather of matters outside nature than of natural phenomena following nature s general laws。They appear to conceive man to be situated in nature as a kingdom within a kingdom；for they believe that he disturbs rather than follows nature s order，that he has absolute control o-ver his actions，and that he is determined solely by himself。They attribute human infir-mities and fickleness，not to the power of nature in general，but to some mysterious flaw in the nature of man，which accordingly they bemoan，deride，despise，or，as usually happens，abuse；he，who succeeds in hitting off the weakness of the human mind more eloquently or more acutely than his fellows，is looked upon as a seer。Still there has been no lack of very excellent men（to whose toil and industry I confess myself much in-debted），who have written many noteworthy things concerning the right way of life，and have given much sage advice to mankind。But no one，so far as I know，has defined the nature and strength of the emotions，and the power of the mind against them for their re-straint。
I do not forget，that the illustrious Descartes，though he believed，that the mind has absolute power over its actions，strove to explain human emotions by their primary causes，and，at the same time，to point out a way，by which the mind might attain to absolute dominion over them。However，in my opinion，he accomplishes nothing beyond a display of the acuteness of his own great intellect，as I will show in the Proper place。For the present I wish to revert to those，who would rather abuse or deride human emo-tions than understand them。Such persons will，doubtless think it strange that I should attempt to treat of human vice and folly geometrically，and should wish to set forth with rigid reasoning those matters which they cry out against as repugnant to reason，frivo-lous，absurd，and dreadful。However，such is my plan。Nothing comes to pass in na-ture，which can be set down to a flaw therein；for nature is always the same，and every-where one and the same in her efficacy and power of action；that is，nature s laws and ordinances，whereby all things come to pass and change from one form to another，are everywhere and always the same；so that there should be one and the same method of understanding the nature of all things whatsoever，namely，through nature s universal laws and rules。Thus the passions of hatred，anger，envy，and so on，considered in themselves，follow from this same necessity and efficacy of nature；they answer to cer-tain definite causes，through which they are understood，and possess certain Properties as worthy of being known as the Properties of anything else，whereof the contemplation in itself affords us delight。I shall，therefore，treat of the nature and strength of the emo-tions according to the same method，as I employed heretofore in my investigations con-cerning God and the mind。I shall consider human actions and desires in exactly the same manner，as though I were concerned with lines，planes，and solids。
Definitions
1.By an adequate cause，I mean a cause through which its effect can be clearly and distinctly perceived。By an inadequate or partial cause，I mean a cause through which，by itself，its effect cannot be understood。
2.I say that we act when anything takes place，either within us or externally to us，whereof we are the adequate cause；that is when through our nature something takes place within us or externally to us，which can through our nature alone be clearly and distinctly understood。On the other hand，I say that we are passive as regards something when that something takes place within us，or follows from our nature externally，we be-ing only the partial cause。
3.By emotion I mean the modifications of the body，whereby the active power of the said body is increased or diminished，aided or constrained，and also the ideas of such modifications。
Therefore，if we can be the adequate cause of any of these modifications，I then call the emotion an activity；otherwise I call it a passion，or state wherein the mind is passive。
Postulates
1.The human body can be affected in many ways，whereby its power of activity is increased or diminished，and also in other ways which do not render its power of activity either greater or less。
2.The human body can undergo many changes，and，nevertheless，retain the im-pressions or traces of objects，and，consequently，the same images of things。
Propositions
PROP。1.Our mind is in certain cases active，and in certain cases passive。In so far as it has adequate ideas it is necessarily active，and in so far as it has inadequate i-deas，it is necessarily passive。
Proof。-In every human mind there are some adequate ideas，and some ideas that are fragmentary and confused。Those ideas which are adequate in the mind are adequate also in God，inasmuch as he constitutes the essence of the mind，and those which are inadequate in the mind are likewise adequate in God，not inasmuch as he contains in himself the essence of the given mind alone，but as he，at the same time，contains the minds of other things。Again，from any given idea some effect must necessarily follow；of this effect God is the adequate cause，not inasmuch as he is infinite，but inasmuch as he is conceived as affected by the given idea。But of that effect whereof God is the cause，inasmuch as he is affected by an idea which is adequate in a given mind，of that effect，I repeat，the mind in question is the adequate cause。Therefore our mind，in so far as it has adequate ideas，is in certain cases necessarily active；this was our first point。Again，whatsoever necessarily，follows from the idea which is adequate in God，not by virtue of his possessing in himself the mind of one man only，but by virtue of his containing，together with the mind of that one man，the minds of other things also，of such an effect the mind of the given man is not an adequate，but only a partial cause；thus the mind，inasmuch as it has inadequate ideas，is in certain cases necessarily pas-sive；this was our second point。Therefore our mind，＆c。
Corollary。-Hence it follows that the mind is more or less liable to be acted upon，in Proportion as it possesses inadequate ideas，and，contrariwise，is more or less active in Proportion as it possesses adequate ideas。
PROP。2.Body cannot determine mind to think，neither can mind determine body to motion or rest or any state different from these，if such there be。
Proof。-All modes of thinking have for their cause God，by virtue of his being a thinking thing，and not by virtue of his being displayed under any other attribute。That，therefore，which determines the mind to thought is a mode of thought，and not a mode of extension；that is，it is not body。This was our first point。Again，the motion and rest of a body must arise from another body，which has also been determined to a state of mo-tion or rest by a third body，and absolutely everything which takes place in a body must spring from God，in so far as he is regarded as affected by some mode of extension，and not by some mode of thought；that is，it cannot spring from the mind，which is a mode of thought。This was our second point。Therefore body cannot determine mind，＆c。
PROP。3.The activities of the mind arise solely from adequate ideas；the passive states of the mind depend solely on inadequate ideas。
Proof。-The first element，which constitutes the essence of the mind，is nothing else but the idea of the actually existent body，which is compounded of many other ide-as，whereof some are adequate and some inadequate。Whatsoever therefore follows from the nature of mind，and has mind for its proximate cause，through which it must be un-derstood，must necessarily follow either from an adequate or from an inadequate idea。But in so far as the mind has inadequate ideas，it is necessarily passive；wherefore the activities of the mind follow solely from adequate ideas，and accordingly the mind is only passive in so far as it has inadequate ideas。
Note。-Thus we see，that passive states are not attributed to the mind，except in so far as it contains something involving negation，or in so far as it is regarded as a part of nature，which cannot be clearly and distinctly perceived through itself without other parts；I could thus show，that passive states are attributed to individual things in the same way that they are attributed to the mind，and that they cannot otherwise be per-ceived，but my purpose is solely to treat of the human mind。
PROP。4.Nothing can be destroyed，except by a cause external to itself。
Proof。-This Proposition is self-evident，for the definition of anything affirms the essence of that thing，but does not negative it；in other words，it postulates the essence of the thing，but does not take it away。So long therefore as we regard only the thing it-self，without taking into account external causes，we shall not be able to find in it any-thing which could destroy it。
PROP。5.Things are naturally contrary，that is，cannot exist in the same object，in so far as one is capable of destroying the other。
Proof。-If they could agree together or co-exist in the same object，there would then be in the said object something which could destroy it；but this，by the foregoing Proposition，is absurd，therefore things。
PROP。6.Everything，in so far as it is in itself，endeavours to persist in its own being。
Proof。-Individual things are modes whereby the attributes of God are expressed in a given determinate manner；that is，they are things which express in a given determi-nate manner the power of God，whereby God is and acts；now no thing contains in itself anything whereby it can be destroyed，or which can take away its existence；but contra-riwise it is opposed to all that could take away its existence。Therefore，in so far as it can，and in so far as it is in itself，it endeavours to persist in its own being。
PROP。7.The endeavour，wherewith everything endeavours to persist in its own being，is nothing else but the actual essence of the thing in question。
Proof。-From the given essence of any thing certain consequences necessarily fol-low，nor have things any power save such as necessarily follows from their nature as de-termined；wherefore the power of any given thing，or the endeavour whereby，either a-lone or with other things，it acts，or endeavours to act，that is，the power or endeavour，wherewith it endeavours to persist in its own being，is nothing else but the given or actu-al essence of the thing in question。
PROP。8.The endeavour，whereby a thing endeavours to persist in its being，in-volves no finite time，but an indefinite time。
Proof。-If it involved a limited time，which should determine the duration of the thing，it would then follow solely，from that power whereby the thing exists，that the thing could not exist beyond the limits of that time，but that it must be destroyed；but this is absurd。Wherefore the endeavour wherewith a thing exists involves no definite time；but，contrariwise，since it will by the same power whereby it already exists always continue to exist，unless it be destroyed by some external cause，this endeavour involves an indefinite time。
PROP。9.The mind，both in so far as it has clear and distinct ideas，and also in so far as it has confused ideas，endeavours to persist in its being for an indefinite period，and of this endeavour it is conscious。
Proof。-The essence of the mind is constituted by adequate and inadequate ideas，therefore，both in so far as it possesses the former，and in so far as it possesses the lat-ter，it endeavours to persist in its own being，and that for an indefinite time。Now as the mind is necessarily conscious of itself through the ideas of the modifications of the body，the mind is therefore conscious of its own endeavour。
Note。-This endeavour，when referred solely to the mind，is called will，when re-ferred to the mind and body in conjunction it is called appetite；it is，in fact，nothing else but man s essence，from the nature of which necessarily follow all those results which tend to its preservation；and which man has thus been determined to perform。
Further，between appetite and desire there is no difference，except that the term desire is generally applied to men，in so far as they are conscious of their appetite，and may accordingly be thus defined：Desire is appetite with consciousness thereof。It is thus plain from what has been said，that in no case do we strive for，wish for，long for，or desire anything，because we deem it to be good，but on the other hand we deem a thing to be good，because we strive for it，wish for it，long for it，or desire it。
PROP。10.An idea，which excludes the existence of our body，cannot be postula-ted in our mind，but is contrary thereto。
Proof。-Whatsoever can destroy our body，cannot be postulated therein。Therefore neither can the idea of such a thing occur in God，in so far as he has the idea of our body；that is，the idea of that thing cannot be postulated as in our mind，but contrari-wise，since the first element，that constitutes the essence of the mind，is the idea of the human body as actually existing，it follows that the first and chief endeavour of our mind is the endeavour to affirm the existence of our body；thus，an idea，which negatives the existence of our body，is contrary to our mind，＆c。
PROP。11.Whatsoever increases or diminishes，helps or hinders the power of ac-tivity in our body，the idea thereof increases or diminishes，helps or hinders the power of thought in our mind。
Proof。-This Proposition is evident from II。7.or from II。14.
PROP。12.The mind，as far as it can，endeavours to conceive those things，which increase or help the power of activity in the body。
Proof。-So long as the human body is affected in a mode，which involves the na-ture of any external body，the human mind will regard that external body as present，and consequently，so long as the human mind regards an external body as present，that is，conceives it，the human body is affected in a mode，which involves the nature of the said external body；thus so long as the mind conceives things，which increase or help the power of activity in our body，the body is affected in modes which increase or help its power of activity；consequently the mind s power of thinking is for that period in-creased or helped。Thus the mind，as far as it can，endeavours to imagine such things。
PROP。13.When the mind conceives things which diminish or hinder the body s power of activity，it endeavours，as far as possible，to remember things which exclude the existence of the first-named things。
Proof。-So long as the mind conceives anything of the kind alluded to，the power of the mind and body is diminished or constrained；nevertheless it will continue to con-ceive it，until the mind conceives something else，which excludes the present existence thereof；that is，the power of the mind and of the body is diminished，or constrained，until the mind conceives something else，which excludes the existence of the former thing conceived；therefore the mind，as far as it can，will endeavour to conceive or re-member the latter。
Corollary。-Hence it follows，that the mind shrinks from conceiving those things，which diminish or constrain the power of itself and of the body。
Note。-From what has been said we may，clearly understand the nature of Love and Hate。Love is nothing else but pleasure accompanied by the idea，of an external cause：Hate is nothing else but pain accompanied by the idea of an external cause。We further see，that he who loves necessarily endeavours to have，and to keep present to him，the object of his love；while he who hates endeavours to remove and destroy the object of his hatred。But I will treat of these matters at more length hereafter。
PROP。14.If the mind has once been affected by two emotions at the same time，it will，whenever it is afterwards affected by one of the two，be also affected by the other。
Proof。-If the human body has once been affected by two bodies at once，whenever afterwards the mind conceives one of them，it will straightway remember the other also。But the mind s conceptions indicate rather the emotions of our body than the nature of external bodies；therefore，if the body，and consequently the mind has been once affect-ed by two emotions at the same time，it will，whenever it is afterwards affected by one of the two，be also affected by the other。
PROP。15.Anything can，accidentally，be the cause of pleasure，pain，or desire。
Proof。-Let it be granted that the mind is simultaneously affected by two emotions，of which one neither increases nor diminishes its power of activity，and the other does either increase or diminish the said power。From the foregoing Proposition it is evident that，whenever the mind is afterwards affected by the former，through its true cause，which（by hypothesis）neither increases nor diminishes its power of action，it will be at the same time affected by the latter，which does increase or diminish its power of activi-ty，that is it will be affected with pleasure or pain。Thus the former of the two emotions will，not through itself，but accidentally，be the cause of pleasure or pain。In the same way also it can be easily shown，that a thing may be accidentally the cause of de-sire。
Corollary。-Simply from the fact that we have regarded a thing with the emotion of pleasure or pain，though that thing be not the efficient cause of the emotion，we can ei-ther love or hate it。
Proof。-For from this fact alone it arises，that the mind afterwards conceiving the said thing is affected with the emotion of pleasure or pain，that is，according as the pow-er of the mind and body may be increased or diminished，＆c。；and consequently，ac-cording as the mind may desire or shrink from the conception of it，in other words，ac-cording as it may love or hate the same。
Note。-Hence we understand how it may happen，that we love or hate a thing without any cause for our emotion being known to us；merely，as the phrase is，from sympathy or antipathy。We should refer to the same category those objects，which affect us pleasurably or painfully，simply because they resemble other objects which affect us in the same way。This I will show in the next Prop。I am aware that certain authors，who were the first to introduce these terms“sympathy”and“antipathy”，wished to sig-nify thereby some occult qualities in things；nevertheless I think we may be permitted to use the same terms to indicate known or manifest qualities。
PROP。16.Simply from the fact that we conceive，that a given object has some point of resemblance with another object which is wont to affect the mind pleasurably or painfully，although the point of resemblance be not the efficient cause of the said emo-tions，we shall still regard the first-named object with love or hate。
Proof。-The point of resemblance was in the object（by hypothesis），when we re-garded it with pleasure or pain，thus，when the mind is affected by the image thereof，it will straightway be affected by one or the other emotion，and consequently the thing，which we perceive to have the same point of resemblance，will be accidentally a cause of pleasure or pain。Thus，although the point in which the two objects resemble one anoth-er be not the efficient cause of the emotion，we shall still regard the first-named object with love or hate。
PROP。17.If we conceive that a thing，which is wont to affect us painfully，has any point of resemblance with another thing which is wont to affect us with an equally strong emotion of pleasure，we shall hate the first-named thing，and at the same time we shall love it。
Proof。-The given thing is（by hypothesis）in itself a cause of pain，and，in so far as we imagine it with this emotion，we shall hate it；further，inasmuch as we conceive that it has some point of resemblance to something else，which is wont to affect us with an equally strong emotion of pleasure，we shall with an equally strong impulse of pleas-ure love it；thus we shall both hate and love the same thing。
Note。-This disposition of the mind，which arises from two contrary emotions，is called vacillation；it stands to the emotions in the same relation as doubt does to the i-magination；vacillation and doubt do not differ one from the other，except as greater dif-fers from less。But we must bear in mind that I have deduced this vacillation from cau-ses，which give rise through themselves to one of the emotions，and to the other acci-dentally。I have done this，in order that they might be more easily deduced from what went before；but I do not deny that vacillation of the disposition generally arises from an object，which is the efficient cause of both emotions。The human body is composed of a variety of individual parts of different nature，and may therefore be affected in a variety of different ways by one and the same body；and contrariwise，as one and the same thing can be affected in many ways，it can also in many different ways affect one and the same part of the body。Hence we can easily conceive，that one and the same object may be the cause of many and conflicting emotions。