42 THE GRAMMAR OF SCIENCE 



S 2. — Sense-Impressions and Consciousness 



This conception of reality as based upon sense- 

 impressions requires careful consideration and some reser- 

 vations and modifications. Let us examine a little more 

 closely what we are to understand by the word sense- 

 impression. In turning round quickly in my chair, I 

 knock my knee against a sharp edge of the table. 

 Without any thought of what I am doing my hand moves 

 down and rubs the bruised part, or the knee may cause 

 me so much discomfort that I get up, think of what I 

 shall do, and settle to apply some arnica. Now the two 

 actions on my part appear of totally different character — 

 at least on first examination. In both cases physiologists 

 tells us that as a primary stage a message is carried from 

 the affected part by what is termed a sensory nerve to the 

 brain. The manner in which this nerve conveys its 

 message is without doubt physical, although its exact 

 modus operandi is still unknown. At the brain what we 

 term the sense-impression is formed, and there most 

 probably some physical change takes place which remains 

 with a greater or less degree of persistence in the case of 

 those stored sense-impressions which we term memories. 

 Everything up to the receipt of the sense-impression by 

 the brain is what we are accustomed to term physical or 

 mechanical, it is a legitimate inference to suppose that 

 what from the psychical aspect we term memory has 

 also a physical side, that the brain takes for every memory 

 a permanent physical impress, whether by change in the 

 molecular constitution or in the elementary motions of the 

 brain-substance, and that such physical impress is the 

 source of our stored sense-impression.^ These physical im- 

 presses play an important part in the manner in which 

 future sense-impressions of a like character are received. 

 If these immediate sense-impressions be of sufficient 

 strength, or amplitude as we might perhaps venture to say, 



1 The closest physical analogies to the "permanent impresses" termed 

 memory are the set and after-strain of the elastician. To assert that they are 

 more than analogies would be to usurp the function of the physiologist. 



