36 
APPLICATION OF THE 
spects his attributes, they are of weight; but are then to 
be taken in conjunction (the attention is not to rest upon 
them, but they are to be taken in conjunction) with the 
unexceptionable evidences which we possess, of skill, 
power, and benevolence, displayed in other instances; 
which evidences may, in strength, number, and variety, be 
such, and may so overpower apparent blemishes, as to in¬ 
duce us, upon the most reasonable ground, to believe, that 
these last ought to be referred to some cause, though we 
be ignorant of it, other than defect of knowledge or of be¬ 
nevolence in the author. 
II. There may be also parts of plants and animals, as 
there were supposed to be of the watch, of which, in some 
instances, the operation, in others, the use, is unknown. 
These form different causes; for the operation may be un¬ 
known, yet the use be certain. Thus it is with the lungs of 
animals. Itdoesnot, I think, appear, that we are acquainted 
with the action of the air upon the blood, or in what man¬ 
ner that action is communicated by the lungs; yet we find 
that a very short suspension of their office destroys the 
life of the animal. In this case, therefore, we maybe said 
to know the use, nay we experience the necessity, of the 
organ, though we be ignorant of its operation. Nearly the 
same thing may be observed of what is called the lympha¬ 
tic system. We suffer grievous inconveniences from its dis¬ 
order, without being informed of the office which it sus¬ 
tains in the economy of our bodies. There may possibly 
also be some few examples of the second class, in which 
not only the operation is unknown, but in which experi¬ 
ments may seem to prove that the part is not necessary; 
or may leave a doubt, how far it is even useful to the plant 
or animal in which it is found. This is said to be the case 
with the spleen; which has been extracted from dogs, with¬ 
out any sensible injury to their vital function. Instances 
rvf *he former kind, namely, in which we cannot explain 
the operation, may be numerous; for they will be so in 
proportion to our ignorance. They will be more or fewer 
to different persons, and in different stages of science. 
Every improvement of knowledge diminishes their number. 
There is hardly, perhaps, a year passes that does not, in 
the works of nature, bring some operation, or some mode 
of operation, to light, which was before undiscovered,—pro¬ 
bably unsuspected. Instances of the second kind, namely, 
where the part appears to be totally useless, I believe to be 
extremely rare; compared with the number of those of 
which the use is evident, they are beneath any assignable 
