ANNUAL ADDRESS. 
107 
of their preconceived ideas. They thought the monkey was there 
and then pre-saw it. 
In the same way, if we expect any natural phenomenon to 
happen, we therefore often think it is happening. 
2. Mistakes of the Senses. This, of course, is a known 
source of fallacy. Our eyes are easily deluded, especially as to 
size and distance. Estimation of the height of a top hat, of a 
man's breadth across the shoulders, of certain colours, of rapidity 
of movement are all very apt to be erroneous. Hence the great 
importance of measurement, emphasized by the saying, "Science 
is, measurement." 
The curious delusions of sight are well illustrated by showing 
people any object, letting them look at it well, and then taking it 
away and asking them to describe it or draw it. The several 
descriptions are very striking examples of how differently a thing 
appears to different people. 
Here, again, previous knowledge makes all the difference ; if we 
know our object before, a short examination may enable us to give 
a very accurate description or representation. So it has been said 
that to Newton and Newton's dog "Diamond" what a different 
Universe appeared, although the picture on the retina was probably 
the same in both. 
Deficiency of one or more senses, even if the others are acute 
enough, seems to lead to imperfect judgment. The senses help 
each other, so that smell without sight, for example, seems to be 
severely handicapped 
3. Delay in Registering Our Impressions. This has lead 
many of us into difficulties. It is very noticeable in reports of 
medical and surgical cases, for instance. I once operated on a 
patient at the Infirmary, and the Resident Officer who wrote out 
the report deferred it for two days. When it was done it departed 
so far from the fact that I could not recognise the description as in 
any way a report of what I had done. 
I have noticed in my diary that if a slight delay occurs I have 
great difficulty in giving a correct description of any natural 
phenomenon. 
Hence it is of great importance to make your notes on the spot. 
These three — bias, mistakes of the senses, and delay in registering 
impressions — lead to much exaggeration and incorrectness in other 
ways. 
There is a method of looking at nature, a mental attitude 
towards it, which we may call the Poetic Attitude. This is too 
large a subject to deal fully with, but it is immensely important, 
and we must say something about it. 
I may say at once that it may easily become a source of danger, 
and cannot be looked upon as an ally of the real naturalist unless 
carefully handled. It can, moreover, seldom be used to prosaic 
people without misleading them. 
