on sound
scientific knowledge is sure to have a corresponding value; and that
which is a mere hasty random guess is likely to have but little value.
Every great step in our progress in discovering causes has been made
in exactly the same way as that which I have detailed to you. A person
observing the occurrence of certain facts and phenomena asks, naturally
enough, what process, what kind of operation known to occur in nature
applied to the particular case, will unravel and explain the mystery?
Hence you have the scientific hypothesis; and its value will be
proportionate to the care and completeness with which its basis had been
tested and verified. It is in these matters as in the commonest affairs
of practical life: the guess of the fool will be folly, while the guess
of the wise man will contain wisdom. In all cases, you see that the
value of the result depends on the patience and faithfulness with
which the investigator applies to his hypothesis every possible kind of
verification.

I dare say I may have to return to this point by-and-by; but having
dealt thus far with our logical methods, I must now turn to something
which, perhaps, you may consider more interesting, or, at any rate,
more tangible. But in reality there are but few things that can be more
important for you to understand than the mental processes and the means
by which we obtain scientific conclusions and theories. [1] Having
granted that the inquiry is a proper one, and having determined on
the nature of the methods we are to pursue and which only can lead to
success, I must now turn to the consideration of our knowledge of the
nature of the processes which have resulted in the present condition of
organic nature.

Here, let me say at once, lest some of you misunderstand me, that I have
extremely little to report. The question of how the present condition of
organic nature came about, resolves itself into two questions. The first
is: How has organic or living matter commenced its existence? And the
second is: How has it been perpetuated? On the second question I shall
have more to say hereafter. But on the first one, what I now have to say
will be for the most part of a negative character.

If you consider what kind of evidence we can have upon this matter, it
will resolve itself into two kinds. We may have historical evidence and
we may have experimental evidence. It is, for example, conceivable, that
inasmuch as the hardened mud which forms a