846 



SCIENCE. 



[N. S. Vol. III. No. 75. 



testify to these two elements. At tlie last 

 meeting of the National Academy I presented a 

 paper on this subject, from which I extract the 

 opening paragraphs, as follows : 



All operations of the mind are judgments. On ex- 

 amining tlie natxire of the judgments we discover two 

 elements or functions, consciousness and inference. 

 Consciousness is awareness of self and change in self, 

 and inference is a guess at the cause of the change. 

 We can discover these functions or elements in all of 

 the judgments of mind. I am conscious of a sound; I 

 infer that it is the voice of a friend. I am conscious 

 of an odor, and infer that it is caused by a rose. I 

 am conscious of a flavor, and I infer that it is the taste 

 of an apple. I am conscious of a sense impression of 

 color, and I infer that it is caused by a tree. These 

 judgments may be erroneous and I may believe in il- 

 lusions, but in every case a judgment is formed, 

 whether correct or incorrect. The condition under 

 which judgments produce illusions or certitudes will 

 hereafter be set forth. That which we have to con- 

 sider now is that in every mentation, whether true or 

 false, as in the perceptions mentioned, there is a con- 

 sciousness and an inference. It will be noticed that 

 we have defined the term consciousness as awareness 

 of change in self, and to this definition we shall ad- 

 here. The word is used in many other senses, but in 

 science it becomes necessarj' to use words with a 

 single meaning. For examjile, we might use the 

 term consciousness to mean also the cognition of self 

 or another, and it is often used in this manner as a 

 general synonym for cognition, but we must have 

 some term to designate awareness of the change in 

 self and select the word consciousness for that pur- 

 pose, as that seems to be its fundamental meaning. 



A consciousness is awareness of change in self, so 

 inference is the interpretation of the meaning of 

 that change. A change has been efiected upon my 

 organ of hearing, and I am conscious of a sound and 

 interpret it as a voice; this interpretation is inference. 

 It is not a random guess, but a guess dictated by 

 experience or some collateral circumstance which 

 suggests this guess. Consciousness, therefore, is not 

 only independent, but it is also absolute in the sense 

 that it must have reality as a change in self ; the in- 

 ference is not only dependent, but it is also subject to 

 error. It may be a certitude or it may be an illusion. 

 Thus, there is either a certitude or an illusion pro- 

 duced by an inference. How then does the mind dis- 

 tinguish between certitudes and illusions ? Here we 

 have to consider cognition. 



Verification is the proof of the inference by expe- 

 rience. Cognition is composed of three functions: 

 consciousness, inference, and verification. That 



which is produced by cognition is certitude. A 

 judgment is composed of two functions — consciousness 

 and inference; if- verification is added by experience 

 it becomes a certitude; if it is not verified by experi- 

 ence it is proved to be an illusion. These may seem 

 very simple propositions and self evident, as they are, 

 yet they are fundamental and must be clearly under- 

 stood in order that proper progress may be made in 

 the study of cognition. 



What I have designated as consciousness and 

 so defined the term Rehmke designates as sub- 

 ject of consciousness ; what I have defined as 

 inference he calls attribute of consciousness. 

 But I go on to use judgment in a restricted 

 sense as based on a consciousness and an infer- 

 ence, and then use cognition as a mentation of 

 three elements — consciousness, inference and 

 verification. As I understand Kehmke's 

 method of defining the two terms of conscious- 

 ness, he makes a valid distinction which is 

 fundamental in psychology and if properly and 

 rigidly observed dispells many illusions in psy- 

 chology, and experimental psychology has abun- 

 dantly demonstrated Rehmke's position. 



I regret that I have not seen Rehmke's book, 

 and on consulting the four papers of Science 

 for last September I do not discover that it was 

 reviewed therein as indicated by his remarks. 



In the judgments formed in the experiment 

 with the two weights the blindfolded man 

 makes a judgment of relative weights; the see- 

 ing man makes a judgment of relative specific 

 weights. Having in advance seen the weights, 

 he has already formed a judgment and uses this 

 judgment of sight in interpreting the conscious- 

 ness experienced through the sense of muscular 

 strain. The psychology of sensation and per- 

 ception cannot be understood or explained 

 without using distinct, definite and understood 

 terms for what I have called consciousness, in- 

 ference, judgment, verification and cognition. 

 What terms shall be used matters little; it may 

 be that Prof. Rehmke's use of subject of con-: 

 sciousuess and attribute of consciousness is 

 wise, but I fear that it will make still greater 

 confusion in a subject which is already burdened 

 with terms, and it seems to me better to follow 

 the example of the physicists in giving re- 

 stricted meanings to words already in use, as in 

 the case of momentum, energy, force and 



