320 S. Tyler on Philosophical Induction. 
from testimony not sufficient to convince the naturalist : he there- 
fore searches for other water-fowl (other testimony ), and finds the 
goose, the pelican, the swan, &c.; and is convinced by this accu- 
mulated testimony, of the general principle, that all water-fowl 
have web-feet. The mental determination is effected by testi- 
mony, and not by rules of logic. The conclusion is not implied 
In the first place, we must separate dew from rain, and the mois- 
ture of fogs, and limit the application of the term to what is re- 
ally meant, which is the spontaneous appearance of moisture on 
substances exposed in the open air, when no rain or visible wet 
is falling. Now, here we have analogous phenomena in the mois- 
ture which bedews a cold metal or stone, when we breathe upon 
it; that which appears on a glass of water fresh from the well in 
arm weather; that which appears on the inside of windows, 
when sudden rain or hail chills the external air; that which runs 
down our walls, when after a long frost, a warm moist thaw 
comes on: all these instances agree in one point, the coldness of 
the object dewed, in comparison with the air in contact with it. 
But in the case of the night dew, is this a real cause? is it a fact, 
that the object dewed is colder than the air? Certainly not, one 
would at first be inclined to say; for what is to make it so? But 
the analogies are cogent and unanimous, and therefore we are not 
to discard their indication; and besides, the experiment is easy : 
we have only to lay a thermometer in contact with the dewed 
substance, and hang one a little distance above it, out of reach of 
on analogy. The analogous instances were the evidence that 
lighted up the path of investigation. And though it is given by 
Herschel as an example of inductive search, without any view to 
the doctrine which I am expounding, yet the analogies are point 
ed out as distinctly, as if it had been written for the very purpose 
for which [ am using it. And this is a fair example of inductive 
search, and points out the true relation of analogy to induction— 
indicates its function in the process. It shows that analogy 18 
the evidence on which the inductive process is conducted. The 
truth is, all the evidence on which the inductive process is con- 
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