# An Essay Concerning Human Understanding/Book II/Chapter XXXI

1. Adequate ideas are such as perfectly represent their archetypes. Of our real ideas, some are adequate, and some are inadequate. Those I call adequate, which perfectly represent those archetypes which the mind supposes them taken from : which it intends them to stand for, and to which it refers them. Inadequate ideas are such, which are but a partial or incomplete representation of those archetypes to which they are referred. Upon which account it is plain,
2. Simple ideas all adequate. First, that all our simple ideas are adequate. Because, being nothing but the effects of certain powers in things, fitted and ordained by God to produce such sensations in us, they cannot but be correspondent and adequate to those powers : and we are sure they agree to the reality of things. For, if sugar produce in us the ideas which we call whiteness and sweetness, we are sure there is a power in sugar to produce those ideas in our minds, or else they could not have been produced by it. And so each sensation answering the power that operates on any of our senses, the idea so produced is a real idea, (and not a fiction of the mind, which has no power to produce any simple idea) ; and cannot but be adequate, since it ought only to answer that power : and so all simple ideas are adequate. It is true, the things producing in us these simple ideas are but few of them denominated by us, as if they were only the causes of them ; but as if those ideas were real beings in them. For, though fire be called painful to the touch, whereby is signified the power of producing in us the idea of pain, yet it is denominated also light and hot ; as if light and heat were really something in the fire, more than a power to excite these ideas in us ; and therefore are called qualities in or of the fire. But these being nothing, in truth, but powers to excite such ideas in us, I must in that sense be understood, when I speak of secondary qualities as being in things ; or of their ideas as being the objects that excite them in us. Such ways of speaking, though accommodated to the vulgar notions, without which one cannot be well understood, yet truly signify nothing but those powers which are in things to excite certain sensations or ideas in us. Since were there no fit organs to receive the impressions fire makes on the sight and touch, nor a mind joined to those organs to receive the ideas of light and heat by those impressions from the fire or sun, there would yet be no more light or heat in the world than there would be pain if there were no sensible creature to feel it, though the sun should continue just as it is now, and Mount Aetna flame higher than ever it did. Solidity and extension, and the termination of it, figure, with motion and rest, whereof we have the ideas, would be really in the world as they are, whether there were any sensible being to perceive them or no : and therefore we have reason to look on those as the real modifications of matter, and such as are the exciting causes of all our various sensations from bodies. But this being an inquiry not belonging to this place, I shall enter no further into it, but proceed to show what complex ideas are adequate, and what not.
3. Modes are all adequate. Secondly, our complex ideas of modes, being voluntary collections of simple ideas, which the mind puts together, without reference to any real archetypes, or standing patterns, existing anywhere, are and cannot but be adequate ideas. Because they, not being intended for copies of things really existing, but for archetypes made by the mind, to rank and denominate things by, cannot want anything ; they having each of them that combination of ideas, and thereby that perfection, which the mind intended they should : so that the mind acquiesces in them, and can find nothing wanting. Thus, by having the idea of a figure with three sides meeting at three angles, I have a complete idea, wherein I require nothing else to make it perfect. That the mind is satisfied with the perfection of this its idea is plain, in that it does not conceive that any understanding hath, or can have, a more complete or perfect idea of that thing it signifies by the word triangle, supposing it to exist, than itself has, in that complex idea of three sides and three angles, in which is contained all that is or can be essential to it, or necessary to complete it, wherever or however it exists. But in our ideas of substances it is otherwise. For there, desiring to copy things as they really do exist, and to represent to ourselves that constitution on which all their properties depend, we perceive our ideas attain not that perfection we intend : we find they still want something we should be glad were in them ; and so are all inadequate. But mixed modes and relations, being archetypes without patterns, and so having nothing to represent but themselves, cannot but be adequate, everything being so to itself. He that at first put together the idea of danger perceived, absence of disorder from fear, sedate consideration of what was justly to be done, and executing that without disturbance, or being deterred by the danger of it, had certainly in his mind that complex idea made up of that combination : and intending it to be nothing else but what is, nor to have in it any other simple ideas but what it hath, it could not also but be an adequate idea : and laying this up in his memory, with the name courage annexed to it, to signify to others, and denominate from thence any action he should observe to agree with it, had thereby a standard to measure and denominate actions by, as they agreed to it. This idea, thus made and laid up for a pattern, must necessarily be adequate, being referred to nothing else but itself, nor made by any other original but the good liking and will of him that first made this combination.
4. Modes, in reference to settled names, may be inadequate. Indeed another coming after, and in conversation learning from him the word courage, may make an idea, to which he gives the name courage, different from what the first author applied it to, and has in his mind when he uses it. And in this case, if he designs that his idea in thinking should be conformable to the other’s idea, as the name he uses in speaking is conformable in sound to his from whom he learned it, his idea may be very wrong and inadequate : because in this case, making the other man’s idea the pattern of his idea in thinking, as the other man’s word or sound is the pattern of his in speaking, his idea is so far defective and inadequate, as it is distant from the archetype and pattern he refers it to, and intends to express and signify by the name he uses for it ; which name he would have to be a sign of the other man’s idea, (to which, in its proper use, it is primarily annexed), and of his own, as agreeing to it : to which if his own does not exactly correspond, it is faulty and inadequate.
5. Because then meant, in propriety of speech, to correspond to the ideas in some other mind. Therefore these complex ideas of modes, which they are referred by the mind, and intended to correspond to the ideas in the mind of some other intelligent being, expressed by the names we apply to them, they may be very deficient, wrong, and inadequate ; because they agree not to that which the mind designs to be their archetype and pattern : in which respect only any idea of modes can be wrong, imperfect, or inadequate. And on this account our ideas of mixed modes are the most liable to be faulty of any other ; but this refers more to proper speaking than knowing right.
6. Ideas of substances, as referred to real essences, not adequate. Thirdly, what ideas we have of substances, I have above shown. Now, those ideas have in the mind a double reference : 1. Sometimes they are referred to a supposed real essence of each species of things. 2. Sometimes they are only designed to be pictures and representations in the mind of things that do exist, by ideas of those qualities that are discoverable in them. In both which ways these copies of those originals and archetypes are imperfect and inadequate.
First, it is usual for men to make the names of substances stand for things as supposed to have certain real essences, whereby they are of this or that species : and names standing for nothing but the ideas that are in men’s minds, they must constantly refer their ideas to such real essences, as to their archetypes. That men (especially such as have been bred up in the learning taught in this part of the world) do suppose certain specific essences of substances, which each individual in its several kinds is made conformable to and partakes of, is so far from needing proof that it will be thought strange if any one should do otherwise. And thus they ordinarily apply the specific names they rank particular substances under, to things as distinguished by such specific real essences. Who is there almost, who would not take it amiss if it should be doubted whether he called himself a man, with any other meaning than as having the real essence of a man ? And yet if you demand what those real essences are, it is plain men are ignorant, and know them not. From whence it follows, that the ideas they have in their minds, being referred to real essences, as to archetypes which are unknown, must be so far from being adequate that they cannot be supposed to be any representation of them at all. The complex ideas we have of substances are, as it has been shown, certain collections of simple ideas that have been observed or supposed constantly to exist together. But such a complex idea cannot be the real essence of any substance ; for then the properties we discover in that body would depend on that complex idea, and be deducible from it, and their necessary connexion with it be known ; as all properties of a triangle depend on, and, as far as they are discoverable, are deducible from the complex idea of three lines including a space. But it is plain that in our complex ideas of substances are not contained such ideas, on which all the other qualities that are to be found in them do depend. The common idea men have of iron is, a body of a certain colour, weight, and hardness ; and a property that they look on as belonging to it, is malleableness. But yet this property has no necessary connexion with that complex idea, or any part of it : and there is no more reason to think that malleableness depends on that colour, weight, and hardness, than that colour or that weight depends on its malleableness. And yet, though we know nothing of these real essences, there is nothing more ordinary than that men should attribute the sorts of things to such essences. The particular parcel of matter which makes the ring I have on my finger is forwardly by most men supposed to have a real essence, whereby it is gold ; and from whence those qualities flow which I find in it, viz. its peculiar colour, weight, hardness, fusibility, fixedness, and change of colour upon a slight touch of mercury, &c. This essence, from which all these properties flow, when I inquire into it and search after it, I plainly perceive I cannot discover : the furthest I can go is, only to presume that, it being nothing but body, its real essence or internal constitution, on which these qualities depend, can be nothing but the figure, size, and connexion of its solid parts ; of neither of which having any distinct perception at all can I have any idea of its essence : which is the cause that it has that particular shining yellowness ; a greater weight than anything I know of the same bulk ; and a fitness to have its colour changed by the touch of quicksilver. If any one will say, that the real essence and internal constitution, on which these properties depend, is not the figure, size, and arrangement or connexion of its solid parts, but something else, called its particular form, I am further from having any idea of its real essence than I was before. For I have an idea of figure, size, and situation of solid parts in general, though I have none of the particular figure, size, or putting together of parts, whereby the qualities above mentioned are produced ; which qualities I find in that particular parcel of matter that is on my finger, and not in another parcel of matter, with which I cut the pen I write with. But, when I am told that something besides the figure, size, and posture of the solid parts of that body in its essence, something called substantial form, of that I confess I have no idea at all, but only of the sound form ; which is far enough from an idea of its real essence or constitution. The like ignorance as I have of the real essence of this particular substance, I have also of the real essence of all other natural ones : of which essences I confess I have no distinct ideas at all ; and, I am apt to suppose, others, when they examine their own knowledge, will find in themselves, in this one point, the same sort of ignorance.
7. Because men know not the real essences of substances. Now, then, when men apply to this particular parcel of matter on my finger a general name already in use, and denominate it gold, do they not ordinarily, or are they not understood to give it that name, as belonging to a particular species of bodies, having a real internal essence ; by having of which essence this particular substance comes to be of that species, and to be called by that name ? If it be so, as it is plain it is, the name by which things are marked as having that essence must be referred primarily to that essence ; and consequently the idea to which that name is given must be referred also to that essence, and be intended to represent it. Which essence, since they who so use the names know not, their ideas of substances must be all inadequate in that respect, as not containing in them that real essence which the mind intends they should.
8. Ideas of substances, when regarded as collections of their qualities, are all inadequate. Secondly, those who, neglecting that useless supposition of unknown real essences, whereby they are distinguished, endeavour to copy the substances that exist in the world, by putting together the ideas of those sensible qualities which are found coexisting in them, though they come much nearer a likeness of them than those who imagine they know not what real specific essences : yet they arrive not at perfectly adequate ideas of those substances they would thus copy into the their minds : nor do those copies exactly and fully contain all that is to be found in their archetypes. Because those qualities and powers of substances, whereof we make their complex ideas, are so many and various, that no man’s complex idea contains them all. That our complex ideas of substances do not contain in them all the simple ideas that are united in the things themselves is evident, in that men do rarely put into their complex idea of any substance all the simple ideas they do know to exist in it. Because, endeavouring to make the signification of their names as clear and as little cumbersome as they can, they make their specific ideas of the sorts of substance, for the most part, of a few of those simple ideas which are to be found in them : but these having no original precedency, or right to be put in, and make the specific idea, more than others that are left out, it is plain that both these ways our ideas of substances are deficient and inadequate. The simple ideas whereof we make our complex ones of substances are all of them (bating only the figure and bulk of some sorts) powers ; which being relations to other substances, we can never be sure that we know all the powers that are in any one body, till we have tried what changes it is fitted to give to or receive from other substances in their several ways of application : which being impossible to be tried upon any one body, much less upon all, it is impossible we should have adequate ideas of any substance made up of a collection of all its properties.
9. Their powers usually make up our complex ideas of substances. Whosoever first lighted on a parcel of that sort of substance we denote by the word gold, could not rationally take the bulk and figure he observed in that lump to depend on its real essence, or internal constitution. Therefore those never went into his idea of that species of body ; but its peculiar colour, perhaps, and weight, were the first he abstracted from it, to make the complex idea of that species. Which both are but powers ; the one to affect our eyes after such a manner, and to produce in us that idea we call yellow ; and the other to force upwards any other body of equal bulk, they being put into a pair of equal scales, one against another. Another perhaps added to these the ideas of fusibility and fixedness, two other passive powers, in relation to the operation of fire upon it ; another, its ductility and solubility in aqua regia, two other powers, relating to the operation of other bodies, in changing its outward figure, or separation of it into insensible parts. These, or parts of these, put together, usually make the complex idea in men’s minds of that sort of body we call gold.
10. Substances have innumerable powers not contained in our complex ideas of them. But no one who hath considered the properties of bodies in general, or this sort in particular, can doubt that this, called gold, has infinite other properties not contained in that complex idea. Some who have examined this species more accurately could, I believe, enumerate ten times as many properties in gold, all of them as inseparable from its internal constitution, as its colour or weight : and it is probable, if any one knew all the properties that are by divers men known of this metal, there would be an hundred times as many ideas go to the complex idea of gold as any one man yet has in his ; and yet perhaps that not be the thousandth part of what is to be discovered in it. The changes that that one body is apt to receive, and make in other bodies, upon a due application, exceeding far not only what we know, but what we are apt to imagine. Which will not appear so much a paradox to any one who will but consider how far men are yet from knowing all the properties of that one, no very compound figure, a triangle ; though it be no small number that are already by mathematicians discovered of it.
11. Ideas of substances, being got only by collecting their qualities, are all inadequate. So that all our complex ideas of substances are imperfect and inadequate. Which would be so also in mathematical figures, if we were to have our complex ideas of them, only by collecting their properties in reference to other figures. How uncertain and imperfect would our ideas be of an ellipsis, if we had no other idea of it, but some few of its properties ? Whereas, having in our plain idea the whole essence of that figure, we from thence discover those properties, and demonstratively see how they flow, and are inseparable from it.
12. Simple ideas, ektupa, and adequate. Thus the mind has three sorts of abstract ideas or nominal essences :
First, simple ideas, which are ektupa or copies ; but yet certainly adequate. Because, being intended to express nothing but the power in things to produce in the mind such a sensation, that sensation when it is produced, cannot but be the effect of that power. So the paper I write on, having the power in the light (I speak according to the common notion of light) to produce in men the sensation which I call white, it cannot but be the effect of such a power in something without the mind ; since the mind has not the power to produce any such idea in itself : and being meant for nothing else but the effect of such a power, that simple idea is real and adequate ; the sensation of white, in my mind, being the effect of that power which is in the paper to produce it, is perfectly adequate to that power ; or else that power would produce a different idea.
13. Ideas of substances are ektupa, and inadequate. Secondly, the complex ideas of substances are ectypes, copies too ; but not perfect ones, not adequate : which is very evident to the mind, in that it plainly perceives, that whatever collection of simple ideas it makes of any substance that exists, it cannot be sure that it exactly answers all that are in that substance. Since, not having tried all the operations of all other substances upon it, and found all the alterations it would receive from, or cause in, other substances, it cannot have an exact adequate collection of all its active and passive capacities ; and so not have an adequate complex idea of the powers of any substance existing, and its relations ; which is that sort of complex idea of substances we have. And, after all, if we would have, and actually had, in our complex idea, an exact collection of all the secondary qualities or powers of any substance, we should not yet thereby have an idea of the essence of that thing. For, since the powers or qualities that are observable by us are not the real essence of that substance, but depend on it, and flow from it, any collection whatsoever of these qualities cannot be the real essence of that thing. Whereby it is plain, that our ideas of substances are not adequate ; are not what the mind intends them to be. Besides, a man has no idea of substance in general, nor knows what substance is in itself.
14. Ideas of modes and relations are archetypes and cannot be adequate. Thirdly, complex ideas of modes and relations are originals, and archetypes ; are not copies, nor made after the pattern of any real existence, to which the mind intends them to be conformable, and exactly to answer. These being such collections of simple ideas that the mind itself puts together, and such collections that each of them contains in it precisely all that the mind intends that it should, they are archetypes and essences of modes that may exist ; and so are designed only for, and belong only to such modes as, when they do exist, have an exact conformity with those complex ideas. The ideas, therefore, of modes and relations cannot but be adequate.