Page:The New International Encyclopædia 1st ed. v. 11.djvu/623

* KNOWLEDGE. 563 KNOWLEDGE. ■world,' and what in and fcr themselves are the Kuhscribers to il:> nerve exchange it lias no means of ascertaining. . . . The sounds from tele- phone and phonograph correspond to immediate and stored sense-impressions. These sense-ini- jiresoions we project as it were outwards and term the real world outside ourselves. ]5ut the things-inlhemselves which the sense-impressions symbolize, the 'reality.' as the metaphysicians wish to call it, at the other end of the nerve, remains unknown and unknowable." The objection thus admirably stated may be called the p.sycho-physical argument against knowledge of reality. The reply to it can best be introduced with a question: How do we know that the ego is seated at the brain terminals of the sensory nerves? How, indeed, do we know that there are any sensory nerves at all ? If all that we know are sensations, considered as merely sub- jective and psychical, what right have we to talk about brain terminals? A very little reflec- tion will convince any one that without any knowledge of the external world one would never come to think of his own experiences as internal and subjective. We first come to know the ob- jects about us, among others the bodies of our neighbors. By dissection of some of these bodies we come to know that there is a brain in the human head and that there are nerves running from innui'ierable points in the periphery of the human body back to the brain. By observation and experimentation we come to know that cer- tain stimuli apjilied to the ends of certain nerves are followed, or accompanied, by conscious pro- cesses. Because in the case of human subjects any sundering of the nerve is followed by ces.sa- tion of the specific conscious process that ordi- narily is eocirdinated with the stinuilation of the nerve, we reason that the conscious process is only indirectly coordinated with the action of the nerve, and directly with some sort of disturbance in the brain. The only justifiable meaning then of the expression, "the conscious ego of each of us seated at the brain terminals of the .sensory nerves," is 'the unitary complex of conscious pro- cesses that arise when the brain is stimulated.' These processes are not seated at the terminals of the sensory nerves and subsequently ejected into the space oiitside the body. At least no scientific observer has ever found, say. a color- sensation seated at the terminal of his optic nerve and subse(piently extruded into outer sjiace. All this talk about the 'seat' of conscious pro- cesses is the sheerest mythology, if anything else is meant than that very careful research based on I'twirn facts of external stimulus and nerve-dis- turbance has led scientists to locate within the brain the phi/siolotjiral processes with which the psychical processes are correlated. The pxi/ehieal processes are not experimetitaJhi loealed there; and any one who interprets the findings of psycho-physics into a location of psychical pro- cesses at the terminals of sensory nerves is the dupe of a simple and transparent metaphor. But it will be said that if the brain is the last object disturbed before consciousness arises, then oori- sciousness nuist be somewhere in the neighbor- hood of the brain. This contention is oliviously based on the very questionable principle that no object can act at a distance. Even in mere physical action it is by no means certain that the principle is true. A physical body attracts another physical body at vast distances, and it is by no means certain that this action is medi- ated by some intervening ether. But even if it be conceded that the principle is true in mechanical ])liysies, what riglit have we to assume that it is also true in p.sycho-physics ? As psychic pro- cesses are facts, it is necessary to observe them impartially, i.e. without any prepossessions, ia or(ler to find out what principles govern their action. It is very (pjeer science that assumes, to begin with, that they must be subject to a prin- ciple that possibly obtains in the mendy physical world. Now, observation of the fact of visual perception, for example, does not confirm the sup- jKJsition that the color-sensations are at first 'seated' at the terminals of the optic nerves, and that afterwards we 'project' them 'as it were, outuards.' So far as any actual visual experi- ence can be interrogated, the answer always is that color-sensations are .always located in olijects before the eyes. If the case is dilTerent in in- fants, we cannot ascertain that fact directly, but must infer it, and the only principle that would warrant the inference is that doubtful one just discussed, viz. that no object can act at a dis- tance. It is obvious therefore that the session of the ego at the terminals of the sensory nervts must not be used as a proof of the fact that we cannot know anything of the outer world: that session is itself a very dubious inference from known facts of the outer world, viz, anatomi- cal and physiological facts which we come to know in exactly the same way in which we come to know any other facts of that same outer world. We use our senses; and we thoughtfully compare the re.sult-s we get by their use, and after criti- cism come to some conclusion as to the facts. In fine, this whole doctrine of the subjectivity of knowledge is itself only a suicid.al inference from known objective facts. It is suicidal because if it were true the only reasons that can he urged for its truth, viz. certain psycho-physical facts, would be deprived of their validity, inasmuch as these reasons can claim validity only on the ground that they are kiuiirn facts of the objective world. Here, as heretofore, we see that knowledge cannot be impugned without presupposing knowledge. In summary of this criticism of agnostic views, it may be sai<l that no known fact can be consist- ently and logically used to demonstrate the im- possibility of knowledge. Knowledge is a fact as indubitable, as real, as inevitable as any fact of sensation, and the validity of any knowledge cannot be assailed except from the vantage ground of better knowledge. The problem as to the extent of knowledge has absorbed philosophical attention fnnii the time of Kant, who cl.iinied that only phenomena can be known, and th:it ultimate reality is unknow- able. Our previous discussion should now enable us to .see the fallacy of this position. It con- sists in the unwarranted assumption of an ulti- mate reality lying tiehind phenomena, an assump- tion which is necessitated, as we have seen, by ti-ying to carry too far a perfectly valid distinc- tion between phenomena. Between |)lienomena there are differences in degree of reality in the sense that scmie phenomena delude us into expect- ing other phenomena which, however, do not ap- pear, while on the other hand other phenomena do not delude us. Our expectations based on their ajipearance are verified. The phenomena of the former kind are illusions, are 'mere appearances,' are 'unreal.' The unreality is nothing intrinsic.