An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

OR SCIENTIFIC METHOD. 309
greater the extent of agreement, the more justified we
are in accepting the hypothesis as true. The hypothesis
must of course agree entirely with the facts which it
was invented to explain ; but it requires to be compared
with a wider range of facts, and to have a place found
for it in the general body of knowledge bearing on the
subject. And when, by this means, we have found that
it is the only possible supposition which can be made
in the circumstances, and that it is competent to ex
plain the facts in question, we may regard it as fully
established ; and then it may be spoken of as a
"fact."
The student should notice the ambiguities of the words
"fact" and "theory."
"Fact" is frequently used, as we
have used it in previous chapters, to signify what is observ
able by our senses "
"
; and in contrast, theory is frequently
used for an hypothesis which is suggested but not yet estab
lished. Many writers restrict the meaning of "theory" to
"hypotheses which are fully established"; but, none the
less, when a hypothesis is thus established beyond the
possibility of doubt, we tend to speak of it as a
"
fact."
The two meanings of "fact" are not so unrelated as
might appear.
Finally, we must understand that hypotheses are not
limited to science. Even primitive savages, in con
ceiving all living and moving Nature to be possessed
by innumerable ghosts or spirits, were forming an
hypothesis to explain the facts not, of course, with
full consciousness of what they were doing. And
whenever we try to account for anything given to us
by testimony or by perception, we are forming an
hypothesis. But the hypotheses of Common-Sense are
made for practical purposes ; no more is required of
them than that they should answer these purposes, as
they do. The hypotheses of scientific thought are