374 THE CAUSES OF THE XI 
daily life may be of little or no moment as 
affecting the general correctness of the conclusions 
at which we may arrive; but, in a scientific in- 
quiry, a fallacy, great or small, is always of im- 
portance, and is sure to be in the long run 
constantly productive of mischievous, if not fatal 
results. 
Do not ‘allow yourselves to be misled by the 
common notion that an hypothesis is untrustworthy 
simply because it is an hypothesis. It is often 
urged, in respect to some scientific conclusion, 
that, after all, it is only an hypothesis. But what 
more have we to guide us in nine-tenths’ of the 
most important affairs of daily life than hypotheses, 
and often very ill-based ones? So that in science, 
where the evidence of an hypothesis is subjected 
to the most rigid examination, we may rightly 
pursue the same course. You may have hypo- 
theses and hypotheses. A man may say, if he 
likes, that the moon is made of green cheese: 
that isan hypothesis. But another man, who has 
devoted a great deal of time and attention to the 
subject, and availed himself of the most powerful 
telescopes and the results of the observations of 
others, declares that in his opinion it is probably 
composed of materials very similar to those of 
which our own earth is made up: and that is also 
only an hypothesis. But I need not tell you that. 
there is an enormous difference in the value of the 
