SECT。1 Of the Origin of Our Ideas
All the perceptions of the human mind resolve themselves into two distinct kinds，which I shall call IMPRESSIONS and IDEAS。The difference betwixt these consists in the degrees of force and liveliness，with which they strike upon the mind，and make their way into our thought or consciousness。Those perceptions，which enter with most force and violence，we may name impressions：and under this name I prehend all our sensations，passions and emotions，as they make their first appearance in the soul。By ideas I mean the faint images of these in thinking and reasoning；such as，for in-stance，are all the perceptions excited by the present discourse，excepting only those which arise from the sight and touch，and excepting the immediate pleasure or uneasi-ness it may occasion。I believe it will not be very necessary to employ many words in ex-plaining this distinction。Every one of himself will readily perceive the difference betwixt feeling and thinking。The mon degrees of these are easily distinguished；though it is not impossible but in particular instances they may very nearly approach to each other。Thus in sleep，in a fever，in madness，or in any very violent emotions of soul，our ideas may approach to our impressions，As on the other hand it sometimes happens，that our impressions are so faint and low，that we cannot distinguish them from our ideas。But notwithstanding this near resemblance in a few instances，they are in general so very dif-ferent，that no-one can make a scruple to rank them under distinct heads，and assign to each a peculiar name to mark the difference。“注釋1”
There is another division of our perceptions，which it will be convenient to observe，and which extends itself both to our impressions and ideas。This division is into SIMPLE and COMPLEX。Simple perceptions or impressions and ideas are such as admit of no distinction nor separation。The plex are the contrary to these，and may be distin-guished into parts。Though a particular colour，taste，and smell，are qualities all united together in this apple，it is easy to perceive they are not the same，but are at least dis-tinguishable from each other。
Having by these divisions given an order and arrangement to our objects，we may now apply ourselves to consider with the more accuracy their qualities and relations。The first circumstance，that strikes my eye，is the great resemblance betwixt our impressions and ideas in every other particular，except their degree of force and vivacity。The one seem to be in a manner the reflexion of the other；so that all the perceptions of the mind are double，and appear both as impressions and ideas。When I shut my eyes and think of my chamber，the ideas I form are exact representations of the impressions I felt；nor is there any circumstance of the one，which is not to be found in the other。In running over my other perceptions，I find still the same resemblance and representation。Ideas and impressions appear always to correspond to each other。This circumstance seems to me remarkable，and engages my attention for a moment。
Upon a more accurate survey I find I have been carried away too far by the first ap-pearance，and that I must make use of the distinction of perceptions into simple and plex，to limit this general decision，that all our ideas and impressions are resemb-ling。I observe，that many of our plex ideas never had impressions，that correspon-ded to them，and that many of our plex impressions never are exactly copied in ide-as。I can imagine to myself such a city as the New Jerusalem，whose pavement is gold and walls are rubies，though I never saw any such。I have seen Paris；but shall I affirm I can form such an idea of that city，as will perfectly represent all its streets and houses in their real and just proportions？
I perceive，therefore，that though there is in general a great，resemblance betwixt our plex impressions and ideas，yet the rule is not universally true，that they are ex-act copies of each other。We may next consider how the case stands with our simple，perceptions。After the most accurate examination，of which I am capable，I venture to affirm，that the rule here holds without any exception，and that every simple idea has a simple impression，which resembles it，and every simple impression a correspondent i-dea。That idea of red，which we form in the dark，and that impression which strikes our eyes in sun-shine，differ only in degree，not in nature。That the case is the same with all our simple impressions and ideas，it is impossible to prove by a particular enumera-tion of them。
Thus we find，that all simple ideas and impressions resemble each other；and as the plex are formed from them，we may affirm in general，that these two species of perception are exactly correspondent。Having discovered this relation，which requires no farther examination，I am curious to find some other of their qualities。Let us consider how。they stand with regard to their existence，and which of the impressions and ideas are causes，and which effects。
The full examination of this question is the subject of the present treatise；and therefore we shall here content ourselves with establishing one general proposition，That all our simple ideas in their first appearance are deriv d from simple impressions，which are correspondent to them，and which they exactly represent……
From this constant conjunction of resembling perceptions I immediately conclude，that there is a great connexion betwixt our correspondent impressions and ideas，and that the existence of the one has a considerable influence upon that of the other。Such a con-stant conjunction，in such an infinite number of instances，can never arise from chance；but clearly proves a dependence of the impressions on the ideas，or of the ideas on the impressions。That I may know on which side this dependence lies，I consider the order of their first appearance；and find by constant experience，that the simple impressions always take the precedence of their correspondent ideas，but never appear in the contra-ry order。The constant conjunction of our resembling perceptions，is a convincing proof，that the one are the causes of the other；and this priority of the impressions is an equal proof，that our impressions are the causes of our ideas，not our ideas of our，impres-sions。
To confirm this I consider another plain and convincing phenomenon；which is，that，where-ever by any accident the faculties，which give rise to any impressions，are obstructed in their operations，as when one is born blind or deaf；not only the impres-sions are lost，but also their correspondent ideas；so that there never appear in the mind the least traces of either of them。Nor is this only true，where the organs of sensation are entirely destroyed，but likewise where they have never been put in action to produce a particular impression。We cannot form to ourselves a just idea of the taste of a pine ap-ple，without having actually tasted it。
There is however one contradictory phenomenon，which may prove，that it is not absolutely impossible for ideas to go before their correspondent impressions。I believe it will readily be allowed that the several distinct ideas of colours，which enter by the eyes，or those of sounds，which are conveyed by the hearing，are really different from each other，though at the same time resembling。Now if this be true of different colours，it must be no less so of the different shades of the same colour，that each of them pro-duces a distinct idea，independent of the rest。
Suppose therefore a person to have enjoyed his sight for thirty years，and to have bee perfectly well acquainted with colours of all kinds，excepting one particular shade of blue，for instance，which it never has been his fortune to meet with。Let all the different shades of that colour，except that single one，be placed before him，descend-ing gradually from the deepest to the lightest；it is plain，that he will perceive a blank，where that shade is wanting，said will be sensible，that there is a greater distance in that place betwixt the contiguous colours，than in any other。Now I ask，whether it is possi-ble for him，from his own imagination，to supply this deficiency，and raise up to himself the idea of that particular shade，though it had never been conveyed to him by his sen-ses？I believe there are few but will be of opinion that he can；and this may serve as a proof，that the simple ideas are not always derived from the correspondent impressions；though the instance is so particular and singular，that it is scarce worth our observing，and does not merit that for it alone we should alter our general maxim。
But besides this exception，it may not be amiss to remark on this head，that the principle of the priority of impressions to ideas must be understood with another limita-tion，viz。，that as our ideas are images of our impressions，so we can form secondary i-deas，which are images of the primary；as appears from this very reasoning concerning them。This is not，properly speaking，an exception to the rule so much as an explan-ation of it。Ideas produce the images of themselves in new ideas；but as the first ideas are supposed to be derived from impressions，it still remains true，that all our simple i-deas proceed either mediately or immediately，from their correspondent impressions。
This then is the first principle I establish in the science of human nature；nor ought we to despise it because of the simplicity of its appearance。For it is remarkable，that the present question concerning the precedency of our impressions or ideas，is the same with what has made so much noise in other terms，when it has been disputed whether there be any innate ideas，or whether all ideas be derived from sensation and reflexion。
“注釋1”I here make use of these terms，impression and idea，in a sense different from what is usual，and I hope this liberty will be allowed me。Perhaps I rather restore the word，idea，to its original sense，from which Mr。LOCKE had perverted it，in making it stand for all our perceptions。By the terms of impression I would not be understood to express the manner，in which our lively perceptions are produced in the soul，but merely the perceptions themselves；for which there is no particular name either in the English or any other language，that I know of。
SECT。2 Division of the Subject
Since it appears，that our simple impressions are prior to their correspondent ideas，and that the exceptions are very rare，method seems to require we should examine our impressions，before we consider our ideas。Impressions way be divided into two kinds，those of SENSATION and those of REFLEXION。The first kind arises in the soul origi-nally，from unknown causes。The second is derived in a great measure from our ideas，and that in the following order。An impression first strikes upon the senses，and makes us perceive heat or cold，thirst or hunger，pleasure or pain of some kind or other。Of this impression there is a copy taken by the mind，which remains after the impression ceases；and this we call an idea。This idea of pleasure or pain，when it returns upon the soul，produces the new impressions of desire and aversion，hope and fear，which may properly be called impressions of reflexion，because derived from it。These again are copied by the memory and imagination，and bee ideas；which perhaps in their turn give rise to other impressions and ideas。So that the impressions of reflexion are only an-tecedent to their correspondent ideas；but posterior to those of sensation，and derived from them。The examination of our sensations belongs more to anatomists and natural philosophers than to moral；and therefore shall not at present be entered upon。And as the impressions of reflexion，viz。passions，desires，and emotions，which principally deserve our attention，arise mostly from ideas，it will be necessary to reverse that meth-od，which at first sight seems most natural；and in order to explain the nature and prin-ciples of the human mind，give a particular account of ideas，before we proceed to im-pressions。For this reason I have here chosen to begin with ideas。