16 ANIMAL INTELLIGENCE 
viduals are concerned, are possibly beyond solution. 
Such are probably tew in number, and under attack by 
new methods may be rendered still fewer; nevertheless, 
it is healthful for man to say now and then after the 
fullest study—“I do not know.” There are states of 
our minds which no doubt bear a closer approximation 
to those of animals than others, and these should be 
seized upon and analysed, if we would understand the 
mental life of animals. No small part of our psychic 
life differs from that of animals rather in degree than 
in kind. Nothing is to be gained for any cause, how- 
ever, by overstating the case, and it is a mistake to 
claim that between the highest men and the most 
intelligent animals there is not a vast difference, even 
if we do not go so far as to say there is a great gulf 
fixed, as some appear to believe. This is another thing, 
however, from assuming that the same holds for the 
most lowly developed men and the most highly 
developed animals. As to the differences in the latter 
case, there is room for great diversity of opinion in the 
present state of our knowledge. 
Experiments with the lowest classes of men and on 
all kinds of animals are urgently needed. 
In the meantime a modest, enquiring, open state of 
mind is that most becoming and helpful. 
