in this case are essentially like the difficulties which check or thwart any cognitive enterprise. Some things are more difficult to observe than others, and all things are difficult to observe under certain circumstances. This is true of mind in no mysterious or unique way.

§ 9. Sensations of the internal states of the organism itself present a peculiar case, that is of sufficient imporProprio-ceptive tance to receive independent treatment. ConSensations cerning certain happenings within my body, I am, so to speak, the only eye-witness. This circumstance plays a very important part in the unique self-knowledge imputed to the mind, and in particular, I believe, lends specious significance to the self-conscious and introspective experiences which have just been examined. Let us first set down the general facts in the case.

A leading physiologist writes as follows: "Bedded in the surface layer of the organism are numbers of receptor cells constituted in adaptation to the stimuli delivered by environmental agencies. [These receptors the author calls "extero-ceptors."] But the organism itself, like the world surrounding it, is a field of ceaseless change, where internal energy is continually being liberated, whence chemical, thermal, mechanical, and electrical effects appear. It is a microcosm in which forces which can act as stimuli are at work as in the macrocosm around. The deep tissues ... have receptors specific to themselves. The receptors which lie in the depth of the organism are adapted for excitation consonantly with changes going on in the organism itself, particularly in its muscles and their accessory organs (tendons, joints, blood-vessels, etc.). Since in this field the stimuli to the receptors are given by the organism itself, their field may be called the proprio-ceptive field.”1

Now my body lies beyond the periphery of every other body, and can, therefore, be generally observed only by extero-ceptive" organs, such as those of vision, touch, etc.

1 C. S. Sherrington: The Integrative Action of the Nervous System, pp. 129-130.

But while I may also observe myself in this fashion, my proprio-ceptors" enable me alone to know my body in another way. There is no occult reason for this; it is a matter of physiological organization. I am sensible of interior pressure and strain, or of the motion and muscular control of my limbs, in a manner impossible for any other observer, simply because no other observer is nervously connected with them as I am. I alone can be specifically sensible of loss of equilibrium, because my semicircular canals, though visible and tangible to others, have a continuous nervous connection with my brain alone. More important is the fact that I am sensible in a very complex way of states and changes in my visceral, circulatory, and respiratory systems. Here, again, I am possessed of sensations from which other observers are cut off for lack of certain nerve fibres which connect these organs only with my cerebral centres.

Now what is the inference from these facts? In the first place, it is to be observed that these sensations constitute knowledge of the body, and not of mind in the traditional sense. I have a species of cognitive access to the interior of my body from which all other knowers are excluded. My heart palpitates for me as it palpitates for no one else. But as it has never been argued that a physical organism is a thing known only to the mind inhabiting it, let us present the matter in another way. My mind possesses sense-contents that can not be similarly presented in any other mind. I alone can "have" these sensations. But does it follow that you cannot know them? Firstly, there is nothing in the sensation that you cannot know. The peculiar quality of heart-palpitation is known to you in other instances; and the bodily locality which makes it mine is immediately perceived by you. These factors must, it is true, be put together by you, but the result is nevertheless knowledge. And secondly, there is nothing about the sensation that you cannot know even better than I. If I were to follow up the mere presentation of the sensa

tion, and proceed to an adequate knowledge of it, I would necessarily rely on anatomical and physiological methods that have from the first been open to you. Indeed, here I am seriously embarrassed; for as you are cut off from proprio-ceptive sensations of my bodily interior, so I am largely cut off from the extero-ceptive sensations which are much more indispensable to a knowledge of sensestructure and function. In short, certain things are presented in a characteristic way to me alone. I alone can have proprio-ceptive sensations of my own body. In order that you may know the interior of my body it is necessary for you to use your imagination, or some other relatively elaborate process.

Is this what is meant by saying that mind can be known only by itself? If so, then that contention loses all of its momentousness. For this is only a case of a very large class. It may even be contended that all existent things are such as to be presented instantly and simply only to a privileged group of knowers. In so far as spacial, events can be sensibly known only by those who enjoy a certain definable proximity, and in so far as temporal only by contemporaries. But this does not withdraw them from the general field of knowledge. I must use my imagination to know what the East Indian may know by opening his eyes; but my knowledge may none the less exceed his. And furthermore, even if it were granted that proprioceptive sensations can be known only introspectively, I can scarcely believe that those who emphasize the uniquely internal character of mind mean that the mind consists in a confused and partial knowledge of the interior of the physical body!

A word more is necessary to show the full importance of the matter. The experiences on which I most rely for a knowledge of myself as mental agent or subject contain an admixture of proprio-ceptive sensations. The very act of self-consciousness is itself attended by characteristic sensations due to bodily posture and respiratory changes. But

above all, the experience of self-activity or effort is largely made up of sensations of internal motion and strain. These experiences are stereotyped, obscure, and largely accidental. But there is, nevertheless, a propriety not commonly recognized, in regarding the proprio-ceptive experience so far as it goes as really a knowledge of self. For my proprio-ceptive experience is largely a knowledge of my organic action on the environment, and it is this action when construed in a certain manner that really constitutes mental action.1

The Content of

§ 10. As respects the accessibility of my mental contents to your observation, the most important general fact is this: that your observation will be Desire, Memory baffled just in so far as my dealings with the and Thought content of my mind are not peripheral. Contrary to a common philosophical opinion, my purpose, intention, or desire is least likely to escape you. This element of my mind is revealed even in my gross action, in the motions of my body as a whole. Your apprehension of it is as sure and as indispensable to social relations as your apprehension of the physical objects that engage my attention. The content of my purpose, that is, the realization proposed, and my more or less consistent devotion to it, are in your full view, whether you be a historian of character or a familiar companion. It is not, then, the desiderative element in mind that escapes observation, nor is it any such typical element, but all content in so far as the mind's dealings with it do not reach the visible exterior of the body. But what is implied in this very statement?

In the first place, we imply that the content in question

1 Cf. Sherrington, op. cit.: "The other character of the stimulations in this field (the proprio-ceptive) we held to be that the stimuli are given in much greater measure than in the surface field of reception, by actions of the organism itself, especially by mass movement of its parts. . . . The immediate stimulus for the reflex started at the deep receptor is thus supplied by some part of the organism itself as agent" (p. 336). Cf. below, pp. 298-301.

is such as to be knowable by me if I can identify it. Commonly, doubt exists only as to which of several things, all plainly known to you, is at the moment known to me. I may tell you, and when I do, one is selected and the others fall away. Or you may conjecture, and if your conjecture be true you possess the content, though without being sure of the relation to my mind.

But in the second place (and I here anticipate a charge of grave omission) the relation of the content to my mind must be supposed to be objectively and discoverably there, even when I do not acknowledge it by a verbal report. It is impossible to formulate a case of memory, for example, without affirming a connection between the past event which contributes the content and the locally present mind that is recalling it. If I am in fact here and now recollecting a visit to London in 1905, a complex is defined, the essential terms of which are in your plain view. And the connection must be homogeneous with the terms. The past event as it was, must be engaged or dealt with by me as I stand before you. In other words, the original perceptual response must be continued into the present. But this is possible only through the identity of the nervous system. The link of recollection, connecting past and present, lies in a retrospective functioning of my body, which can be accounted for only by its history. And this is as accessible as any natural or moral process. When you know that I am looking at the moon, the salient facts are before you, the focalized posture of my body and its organ of vision, the concentration and consistency of my action, and, most important of all, the moon. In the case of my recollection of London the facts are more complicated, and even in part inaccessible, but equally with the facts just cited, they are in the context of your possible knowledge. They consist in such elements as my central attentive process, certain persisting modifications of my cerebrum, my original dealings, practical and neural, with London, and - London itself.