PRINCIPLES OF BIOLOGY. 
229 
when we descend to particular instances we should expect 
occasionally to find discordances, and to find those dis¬ 
cordances more evident when the comparison lies between 
distinct lines of evolution than when it is made between 
organisms which belong to the same line. In its own line the 
elephant is the most sagacious, and the life which it enjoys is 
higher than that which falls to the lot of any other 
pachyderm. 
In the third place, it seems indisputable that for reckoning 
the degree of life enjoyed by any organism, the mere number 
of years which it passes through is a most fallacious guide. 
We must take account not only of the length of life but also 
of its intensity; and in cases where the vital activity manifests 
itself in the work of the brain as well as in that of the limbs, 
this resolves itself into the statement that the true measure 
of life is the sum of the mental and bodily activities which 
come into play during its continuance. Tried by this test, it 
is plain that not only the life of a Darwin or a Spencer, but 
also the average life of the human race, is superior to that of 
an unspeculative, uncritical elephant. 
In the fourth place, Mr. Tait actually admits the truth of 
the theorem which he imagines he is disputing, for he says 
that man “ enjoys a very much higher form of life than ” the 
elephant, and he implies (what can scarcely be denied) that 
the amount of correspondence with external forces possessed 
by the human organism is greater than that exhibited in the 
elephant, and what is that but to allow that in comparing 
these two cases “ the degree of life varies as the degree of 
correspondence” ? The fact is, Mr. Tait has not made himself 
duly acquainted with the theory which he undertakes to discuss. 
Throughout Chapter vi. the term longevity is nowhere used, 
while passages are abundant * which show that the view of 
“ degree of life ” here taken is that which the great philosopher 
intends. 
In the last place, even if it be granted that a few apparent 
exceptions to his generalisation exist, that is a scarcely 
sufficient ground on which to erect such a sweeping denunci¬ 
ation of Herbert Spencer and all his works. To do this is to 
forget the intricacy and many-sidedness, the interaction and 
counteraction of forces, by which all biological problems are 
pre-eminently distinguished. 
* See p. 84, 1. 12; p. 85, 1. 8; p. 89, 1. 16; p. 90, 1. 5. 
Mr. W. R. Hughes has called my attention to the following passage 
in “Felix Holt,” vol. iii., chap. 49:—“Life is measured by the 
rapidity of change, the succession of influences that modify the being.” 
