PROP。18.A man is as much affected pleasurably or painfully by the image of a thing past or future as by the image of a thing present。
Proof。-So long as a man is affected by the image of anything，he will regard that thing as present，even though it be non-existent，he will not conceive it as past or fu-ture，except in so far as its image is joined to the image of time past or future。Where-fore the image of a thing，regarded in itself alone，is identical，whether it be referred to time past，time future，or time present；that is，the disposition or emotion of the body is identical，whether the image be of a thing past，future，or present。Thus the emotion of pleasure or pain is the same，whether the image be of a thing past or future。
Note 1.-I call a thing past or future，according as we either have been or shall be affected thereby。For instance，according as we have seen it，or are about to see it，ac-cording as it has recreated us，or will recreate us，according as it has harmed us，or will harm us。For，as we thus conceive it，we affirm its existence；that is，the body is af-fected by no emotion which excludes the existence of the thing，and therefore the body is affected by the image of the thing，in the same way as if the thing were actually present。However，as it generally happens that those，who have had many experiences，vacil-late，so long as they regard a thing as future or past，and are usually in doubt about its issue；it follows that the emotions which arise from similar images of things are not so constant，but are generally disturbed by the images of other things，until men become assured of the issue。
Note 2.-From what has just been said，we understand what is meant by the terms Hope，Fear，Confidence，Despair，Joy，and Disappointment。Hope is nothing else but an inconstant pleasure，arising from the image of something future or past，whereof we do not yet know the issue。Fear，on the other hand，is an inconstant pain also arising from the image of something concerning which we are in doubt。If the element of doubt be removed from these emotions，hope becomes Confidence and fear becomes Despair。In other words，Pleasure or Pain arising from the image of something concerning which we have hoped or feared。Again，Joy is Pleasure arising from the image of something past whereof we doubted the issue。Disappointment is the Pain opposed to Joy。
PROP。19.He who conceives that the object of his love is destroyed will feel pain；if he conceives that it is preserved he will feel pleasure。
Proof。-The mind，as far as possible，endeavours to conceive those things which increase or help the body s power of activity；in other words，those things which it loves。But conception is helped by those things which postulate the existence of a thing，and contrariwise is hindered by those which exclude the existence of a thing；therefore the images of things，which postulate the existence of an object of love，help the mind s endeavour to conceive the object of love，in other words，affect the mind pleasurably；contrariwise those things，which exclude the existence of an object of love，hinder the aforesaid mental endeavour；in other words，affect the mind painfully。He，therefore，who conceives that the object of his love is destroyed will feel pain，＆c。
PROP。20.He who conceives that the object of his hate is destroyed will feel pleas-ure。
Proof。-The mind endeavours to conceive those things，which exclude the exist-ence of things whereby the body s power of activity is diminished or constrained；that is，it endeavours to conceive such things as exclude the existence of what it hates；therefore the image of a thing，which excludes the existence of what the mind hates，helps the aforesaid mental effort，in other words，affects the mind pleasurably。Thus he who con-ceives that the object of his hate is destroyed will feel pleasure。
PROP。21.He who conceives，that the object of his love is affected pleasurably or painfully，will himself be affected pleasurably or painfully；and the one or the other e-motion will be greater or less in the lover according as it is greater or less in the thing loved。
Proof。-The images of things which postulate the existence of the object of love，help the mind s endeavour to conceive the said object。But pleasure postulates the exist-ence of something feeling pleasure，so much the more in Proportion as the emotion of pleasure is greater；for it is a transition to a greater perfection；therefore the image of pleasure in the object of love helps the mental endeavour of the lover；that is，it affects the lover pleasurably，and so much the more，in Proportion as this emotion may have been greater in the object of love。This was our first point。Further，in so far as a thing is affected with pain，it is to that extent destroyed，the extent being in Proportion to the amount of pain；therefore he who conceives，that the object of his love is affected pain-fully，will himself be affected painfully，in Proportion as the said emotion is greater or less in the object of love。
PROP。22.If we conceive that anything pleasurably affects some object of our love，we shall be affected with love towards that thing。Contrariwise，if we conceive that it affects an object of our love painfully，we shall be affected with hatred towards it。
Proof。-He，who affects pleasurably or painfully the object of our love，affects us also pleasurably or painfully-that is，if we conceive the loved object as affected with the said pleasure or pain。But this pleasure or pain is postulated to come to us accompa-nied by the idea of an external cause；therefore，if we conceive，that anyone affects an object of our love pleasurably or painfully，we shall le affected with love or hatred to-wards him。
PROP。23.He who conceives，that an object of his hatred is painfully affected，will feel pleasure。Contrariwise，if he thinks that the said object is pleasurably affected，he will feel pain。Each of these emotions will be greater or less，according as its contra-ry is greater or less in the object of hatred。
Proof。-In so far as an object of hatred is painfully affected，it is destroyed，to an extent Proportioned to the strength of the pain。Therefore，he who conceives，that some object of his hatred is painfully affected，will feel pleasure，to an extent Proportioned to the amount of pain he conceives in the object of his hatred。This was our first point。A-gain，pleasure postulates the existence of the pleasurably affected thing，in Proportion as the pleasure is greater or less。If anyone imagines that an object of his hatred is pleasur-ably affected，this conception will hinder his own endeavour to persist；in other words，he who hates will be painfully affected。
Note。-This pleasure can scarcely be felt unalloyed，and without any mental con-flict。For，in so far as a man conceives that something similar to himself is affected by pain，he will himself be affected in like manner；and he will have the contrary emotion in contrary circumstances。But here we are regarding hatred only。
PROP。24.If we conceive that anyone pleasurably affects an object of our hate，we shall feel hatred towards him also。If we conceive that he painfully affects the said ob-ject，we shall feel love towards him。
Proof。-This Proposition is proved in the same way as Part3.22.，which see。
Note。-These and similar emotions of hatred are attributable to envy，which，ac-cordingly，is nothing else but hatred，in so far as it is regarded as disposing a man to re-joice in another s hurt，and to grieve at another s advantage。
PROP。25.We endeavour to affirm，concerning ourselves，and concerning what we love，everything that we conceive to affect pleasurably ourselves，or the loved ob-ject。Contrariwise，we endeavour to negative everything，which we conceive to affect painfully ourselves or the loved object。
Proof。-That，which we conceive to affect an object of our love pleasurably or painfully，affects us also pleasurably or painfully。But the mind endeavours，as far as possible，to conceive those things which affect us pleasurably；in other words，it en-deavours to regard them as present。And，contrariwise，it endeavours to exclude the ex-istence of such things as affect us painfully；therefore，we endeavour to affirm concern-ing ourselves，and concerning the loved object，whatever we conceive to affect our-selves，or the loved object pleasurably。
PROP。26.We endeavour to affirm，concerning that which we hate，everything which we conceive to affect it painfully；and，contrariwise，we endeavour to deny，con-cerning it，everything which we conceive to affect it pleasurably。
Proof。-This Proposition follows from III。23.，as the foregoing Proposition fol-lowed from III。21.
Note。-Thus we see that it may readily happen，that a man may easily think too highly of himself，or a loved object，and，contrariwise，too meanly of a hated object。This feeling is called pride，in reference to the man who thinks too highly of himself，and is a species of madness，wherein a man dreams with his eyes open，thinking that he can accomplish all things that fall within the scope of his conception，and thereupon ac-counting them real，and exulting in them，so long as he is unable to conceive anything which excludes their existence，and determines his own power of action。Pride，there-fore，is pleasure springing from a man thinking too highly of himself。Again，the pleas-ure which arises from a man thinking too highly of another is called over-esteem。Where-as the pleasure which arises from thinking too little of a man is called disdain。
PROP。27.By the very fact that we conceive a thing，which is like ourselves，and which we have not regarded with any emotion，to be affected with any emotion，we are ourselves affected with a like emotion。
Proof。-The images of things are modifications of the human body，whereof the i-deas represent external bodies as present to us；in other words，whereof the ideas in-volve the nature of our body，and，at the same time，the nature of external bodies as present。If，therefore，the nature of the external body be similar to the nature of our body，then the idea which we form of the external body will involve a modification of our own body similar to the modification of the external body。Consequently，if we conceive anyone similar to ourselves as affected by any emotion，this conception will express a modification of our body similar to that emotion。Thus，from the fact of conceiving a thing like ourselves to be affected with any emotion，we are ourselves affected with a like emotion。If，however，we hate the said thing like ourselves，we shall，to that extent，be affected by a contrary，and not similar，emotion。
Note。-This imitation of emotions，when it is referred to pain，is called compas-sion；when it is referred to desire，it is called emulation，which is nothing else but the desire of anything，engendered in us by the fact that we conceive that others have the like desire。
Corollary1.-If we conceive that anyone，whom we have hitherto regarded with no emotion，pleasurably affects something similar to ourselves，we shall be affected with love towards him。If，on the other hand，we conceive that he painfully affects the same，we shall be affected with hatred towards him。
Proof。-This is proved from the last Proposition in the same manner as III。22.is proved from III。21.
Corollary2.-We cannot hate a thing which we pity，because its misery affects us painfully。
Proof。-If we could hate it for this reason，we should rejoice in its pain，which is contrary to the hypothesis。
Corollary3.-We seek to free from misery，as far as we can，a thing which we pity。
Proof。-That，which painfully affects the object of our pity，affects us also with similar pain；therefore，we shall endeavour to recall everything which removes its exist-ence，or which destroys it；in other words，we shall desire to destroy it，or we shall be determined for its destruction；thus，we shall endeavour to free from misery a thing which we pity。
PROP。28.We endeavour to bring about whatsoever we conceive to conduce to pleasure；but we endeavour to remove or destroy whatsoever we conceive to be truly re-pugnant thereto，or to conduce，to pain。
Proof。-We endeavour，as far as possible，to conceive that which we imagine to conduce to pleasure；in other words we shall endeavour to conceive it as far as possible as present or actually existing。But the endeavonr of the mind，or the mind s power of thought，is equal to，and simultaneous with，the endeavour of the body，or the body s power of action。Therefore we make an absolute endeavour for its existence，in other words we desire and strive for it；this was our first point。Again，if we conceive that something，which we believed to be the cause of pain，that is which we hate，is de-stroyed，we shall rejoice。We shall，therefore，endeavour to destroy the same，or to remove it from us，so that we may not regard it as present；this was our second point。Wherefore whatsoever conduces to pleasure，＆c。
PROP。29.We shall also endeavour to do whatsoever we conceive men to regard with pleasure，and contrariwise we shall shrink from doing that which we conceive men to shrink from。
Proof。-From the fact of imagining，that men love or hate anything，we shall love or hate the same thing。That is，from this mere fact we shall feel pleasure or pain at the thing s presence。And so we shall endeavour to do whatever we conceive men to love or regard with pleasure，etc。
Note。-This endeavour to do a thing or leave it undone，solely in order to please men，we call ambition，especially when we so eagerly endeavour to please the vulgar，that we do or omit certain things to our own or another s hurt；in other cases it is gener-ally called kindliness。Furthermore I give the name of praise to the pleasure，with which we conceive the action of another，whereby he has endeavoured to please us；but of blame to the pain wherewith we feel aversion to his action。
PROP。30.If anyone has done something which he conceives as affecting other men pleasurably，he will be affected by pleasure，accompanied by the idea of himself as cause；in other words，he will regard himself with pleasure。On the other hand，if he has done anything which he conceives as affecting others painfully，he will regard him-self with pain。
Proof。-He who conceives，that he affects others with pleasure or pain，will，by that very fact，himself be affected with pleasure or pain，but，as a man is conscious of himself through the modifications whereby he is determined to action，it follows that he who conceives，that he affects others pleasurably，will be affected with pleasure accom-panied by the idea of himself as cause；in other words，will regard himself with pleas-ure。
Note。-As love is pleasure accompanied by the idea of an external cause，and ha-tred is pain accompanied by the idea of an external cause；the pleasure and pain in question will be a species of love and hatred。But，as the terms love and hatred are used in reference to external objects，we will employ other names for the emotions now under discussion；pleasure accompanied by the idea of an external cause we will style Honour，and the emotion contrary thereto we will style Shame；I mean in such cases as where pleasure or pain arises from a man s belief，that he is being praised or blamed：other-wise pleasure accompanied by the idea of an external cause is called self-complacency，and its contrary pain is called repentance。Again，as it may happen that the pleasure，wherewith a man conceives that he affects others，may exist solely in his own imagina-tion，and as everyone endeavours to conceive concerning himself that which he con-ceives will affect him with pleasure，it may easily come to pass that a vain man may be proud and may imagine that he is pleasing to all，when in reality he may be an annoy-ance to all。
PROP。31.If we conceive that anyone loves，desires，or hates anything which we ourselves love，desire，or hate，we shall thereupon regard the thing in question with more steadfast love，＆c。On the contrary，if we think that anyone shrinks from some-thing that we love，we shall undergo vacillation of soul。
Proof。-From the mere fact of conceiving that anyone loves anything we shall our-selves love that thing；but we are assumed to love it already；there is，therefore，a new cause of love，whereby our former emotion is fostered；hence we shall thereupon love it more steadfastly。Again，from the mere fact of conceiving that anyone shrinks from any-thing，we shall ourselves shrink from that thing。If we assume that we at the same time love it，we shall then simultaneously love it and shrink from it；in other words，we shall be subject to vacillation。
Corollary。-From the foregoing，and also from Part 3.28.it follows that everyone endeavours，as far as possible，to cause others to love what he himself loves，and to hate what he himself hates。
Note。-This endeavour to bring it about，that our own likes and dislikes should meet with universal approval，is really ambition；wherefore we see that everyone by na-ture desires，that the rest of mankind should live according to his own individual disposi-tion；when such a desire is equally present in all，everyone stands in everyone else s way，and in wishing to be loved or praised by all，all become mutually hateful。
PROP。32.If we conceive that anyone takes delight in something，which only one person can possess，we shall endeavour to bring it about that the man in question shall not gain possession thereof。
Proof。-From the mere fact of our conceiving that another person takes delight in a thing we shall ourselves love that thing and desire to take delight therein。But we as-sumed that the pleasure in question would be prevented by another s delight in its ob-ject；we shall，therefore，endeavour to prevent his possession thereof。
Note。-We thus see that man s nature is generally so constituted，that he takes pity on those who fare ill，and envies those who fare well with an amount of hatred Propor-tioned to his own love for the goods in their possession。Further，we see that from the same Property of human nature，whence it follows that men are merciful，it follows also that they are envious and ambitious。Lastly，if we make appeal to Experience，we shall find that she entirely confirms what we have said；more especially if we turn our atten-tion to the first years of our life。We find that children，whose body is continually，as it were，in equilibrium，laugh or cry simply because they see others laughing or crying；moreover，they desire forthwith to imitate whatever they see others doing，and to possess themselves whatever they conceive as delighting others；inasmuch as the images of things are，as we have said，modifications of the human body，or modes wherein the hu-man body is affected and disposed by external causes to act in this or that manner。
PROP。33 When we love a thing similar to ourselves we endeavour，as far as we can，to bring about that it should love us in return。
Proof。-That which we love we endeavour，as far as we can，to conceive in prefer-ence to anything else。If the thing be similar to ourselves，we shall endeavour to affect it pleasurably in preference to anything else。In other words，we shall endeavour，as far as we can，to bring it about，that the thing should be affected with pleasure accompanied by the idea of ourselves，that is，that it should love us in return。
PROP。34.The greater the emotion with which we conceive a loved object to be af-fected towards us，the greater will be our complacency。
Proof。-We endeavour，as far as we can，to bring about，that what we love should love us in return；in other words，that what we love should be affected with pleasure ac-companied by the idea of ourself as cause。Therefore，in Proportion as the loved object is more pleasurably affected because of us，our endeavour will be assisted。-that is the greater will be our pleasure。But when we take pleasure in the fact，that we pleasurably affect something similar to ourselves，we regard ourselves with pleasure；therefore the greater the emotion with which we conceive a loved object to be affected，＆c。
PROP。35.If anyone conceives，that an object of his love joins itself to another with closer bonds of friendship than he himself has attained to，he will be affected with hatred towards the loved object and with envy towards his rival。