On Sameness and Identity: A Psychological Study / Being a Contribution to the Foundations of a Theory of Knowledge

by George Stuart Fullerton

What peculiar experience then does the word mark when the observer declares that he has seen the same tree twice?

We are now in the sphere of material objects (i. e., as experienced; I refer to the mental content and nothing more), and are not concerned with our experiences as isolated elements, but as grouped and arranged in series. Our total possible experience of any one object is a collection of partly simultaneous and partly successive actual and possible sensations which condition each other, and which we regard as a unit. The Idealist believes that this is all there is of the object, and all we mean when we commonly employ the word. The Realist assumes that there is something beyond and corresponding to this experience, and which is to be regarded as the real thing. He, however, must admit that all we can know of any object, in whatever sense we choose to employ that word, all our evidence for maintaining its existence and determining its qualities, must be drawn from this group of sensations. It is this that we immediately know, and anything inferred must be inferred from this.

From this it follows that when any one, whether Realist, or Idealist, or unreflective man, feels justified in asserting that what he perceives to-day is the same object he perceived yesterday, he is led to make this assertion on the strength of some distinction in his immediate experience, and he refers only secondarily, if at all, to anything beyond and external to this. The distinction which he marks by the word is this: He has reason to believe that the two percepts in question belong to the one series,—to the one life history, so to speak. He believes that had he cared to do so he could have filled up the gap between them by a continuous series of percepts, each conditioned by the preceding, and forming the one chain. Each represents to him the one object, in that each stands for the whole series, and his thought is much more taken up with the series as a whole than with the individuals composing it. He knows that the percepts in such a series can only be successive, never simultaneous. Had he reason to suspect that the two percepts we are discussing belong to different series of this kind, and that there is nothing in the nature of the case to prevent their being simultaneous, he would decide for two trees.

But each percept contains more than one mental element, and just as we may regard each percept as representing the whole series, so we may regard each element as representing the whole complex which may be experienced at one time, and through this the whole series of percepts. I say that the orange I smell is the same with the one I see; that I can reveal by striking a light the chair I fell over in the dark; that I hear rattling down the street the coach I stepped out of a few moments ago. It is not worth while to distinguish this use from the use of the word same just mentioned, for they agree in making a single experience stand for a whole group or series, which is assumed to be at least potentially present with each one. When we have had two experiences thus representing the one group, we say that we have in two ways, or on two occasions, experienced the same object. In this sense has the man in our illustration seen yesterday and to-day the same tree. In this sense could he at the one time see and touch the same tree.

It is in this sense also that we use the word when we say that the object seen with the naked eye and the object seen through a telescope or under a microscope are the same. If I look at a distant object with the naked eye and then look at it through a telescope, what I actually see (or what is actually in the sense) is in the two cases very different. But just as seeing an object from a distance with the naked eye, I may walk towards it and substitute for the dim and vague percept which I first had a series of percepts increasing in clearness and ending in one which I regard as altogether satisfactory, so I may substitute at once this clear percept for the dim one, by the use of the telescope, and may know that it properly belongs to the series which, taken as a whole, constitutes my notion of the object. This I may know from the relations which this percept bears to the other percepts of the series, and which allow me to pass in my inferences from it to them as I can from any one of them to another. If, seeing a dim object upon the horizon, I raise a telescope and through it perceive the figure of a man, I know that I could have had a similar percept without any telescope by simply approaching the object. Conversely, on perceiving a man near at hand, I know I could have a similar percept from a distance by looking through a telescope. I call the man seen through the telescope the same as the man seen with the naked eye, for the same reason as I call the man seen by the eye at a distance the same with the man seen near at hand.

And the apparently non-extended speck which I see with the naked eye looks very different from the curious insect I see when I place a microscope over this speck, but I call them the same for the reason just given. If the insect as seen under the glass be divided, so is the speck as seen by the eye; if the insect is taken away, the speck disappears too. The series of percepts made possible through the microscope may be regarded as a continuation of the series which arises from approaching the eye to the object. Each member in it stands in a relation to this primary series similar to that illustrated above in the case of the telescope, and similar to that held by the terms of the primary series to each other. It should be kept clearly in mind that in all these cases the object (immediately perceived) is the same only in the sense pointed out, i. e., two or more percepts, which may, in themselves considered, be quite unlike each other, are recognized as in a certain relation to each other, as each representing the one series to which all belong. If one thinks he has reason to believe each percept represents not merely the series of percepts, but something different, which he infers and is pleased to call the "real" thing, he may be inclined to believe that in saying he sees the same object on two occasions he is referring to this something. It must be clear to him, however that all his evidence for the sameness of this something lies in the experience I have described, and it is to this that he must point in proof that it is the same. The percepts themselves are certainly not the same in any other sense than the one given. They are not identical, and they need not be alike. They merely stand for each other. Should one forget this, he will fall into blunders which I will illustrate at length when I speak of the common opinion on the subject of the infinite divisibility of space.

John Locke, in his famous "Essay,"[1] has made a distinction between the sameness of masses of inorganic matter and the sameness of organisms. That of the former, he says, consists in the sameness of their particles, while the sameness of a plant or animal does not consist in that of the particles which compose it at this time or at that, for they are in continual flux, but in the participation in the one life of the organism. It does not, however, appear to me that we have here a real difference in the kind of experience marked by the word. The difference is merely that in the one case we connect this experience, not with the object as a whole, but with the separate particles which compose it, which we take as so many separate objects each having a sameness of the kind just discussed, while in the other case we look upon the object as a whole, as a unit, and disregard any reference to its component parts. But whether we regard the object as a unit or take each of its ultimate parts as separate objects, we are thinking of the one kind of sameness. We are thinking of a certain life-history in which any one link may represent the whole, and any two links may be, from this point of view, regarded as equivalent. It is not merely with reference to plants and animals that we speak of sameness without regard to a sameness of constituent parts. We do it in this case simply because the organism furnishes us with a convenient unit, and one much more important as a unit than as an aggregate. We can make similar units when we please, and consider their sameness without thinking of their parts. We speak of the same nation as existing through many generations, and of the same corporation as surviving many deaths. Whether the object we are considering be naturally indivisible, or composite and assumed a unit for convenience, when we speak of it as the same at two different times we are referring to the one experience. Locke does make here a distinction worth noticing, but it does not mark two fundamentally different uses of the word.

Sec. 5. IV. Two objects are called the same, and two other mental experiences occurring at the one time are called the same, from the fact that they are recognized as alike. The botanist, finding that two plants belong to the one class calls them the same without any intention of confounding the two individuals. Nor does one who places his two hands in warm water and declares that he has the same feeling in both, confound the two streams of sensation. The fact that only likeness is meant is here clearly recognized. It is not, I think, as clearly recognized when similar sensations or other mental experiences (considered singly), occurring at different times, are called the same. In that case they are sometimes spoken of as if they were material objects having a continuous sameness after the fashion explained above.

Sec. 6. V. The word same is used to signify the relation between any mental experience and that which is regarded as its representative. This representative may or may not resemble it. We speak, for example, of calling up in memory this or that object seen at some past time. The memory-image is certainly not the same with the original percept in Sense I. When we say that the object of memory is the past, we cannot mean this, for it is plainly false. Nor is it thought of as merely like it, as in Sense II. It is thought of as a something which represents it—stands for it in a peculiar way. Just what this implies I will not here attempt to discover. It is enough for my purpose to point out that when we say a man remembers an object we do not mean merely to indicate the presence in his imagination of a resembling picture, but to include a certain relation between this picture and an original percept.

It is not easy to describe what is present in an act of memory. When I am thinking of another man as calling to mind something from his past experience, I bring before my own mind two pictures, one representing his original percept, and one his present memory-image. Holding these before me together, I recognize them as related, but distinct. I use the word same to denote their relation. But the person who is exercising his memory does not have before his mind two objects, an original and a copy, with an observed relation between them. He has not the original, or it would not be an act of memory. When, however, he reflects upon his experience as I have done, he represents it to himself as I have represented it to myself. He speaks as if, in the act of remembering, he were conscious of two objects and could compare them. He speaks of recognizing the memory picture as a copy and representative of the original percept. Language, as commonly used, adapts itself to this way of regarding the matter, and I may leave a further analysis of it to the student of the memory, merely pointing out that, whatever is implied in the experience, a common use of the word same is to denote this relation between any mental experience and the memory-image which represents it.