ed, we are in the hands of the physicist and
the astronomer, whose business it is to deal with those questions.

I have now, ladies and gentlemen, arrived at the conclusion of the task
which I set before myself when I undertook to deliver these lectures. My
purpose has been, not to enable those among you who have paid no
attention to these subjects before, to leave this room in a condition to
decide upon the validity or the invalidity of the hypothesis of
evolution; but I have desired to put before you the principles upon
which all hypotheses respecting the history of Nature must be judged;
and furthermore, to make apparent the nature of the evidence and the
amount of cogency which is to be expected and may be obtained from it.
To this end, I have not hesitated to regard you as genuine students and
persons desirous of knowing the truth. I have not shrunk from taking you
through long discussions, that I fear may have sometimed tried your
patience; and I have inflicted upon you details which were
indispensable, but which may well have been wearisome. But I shall
rejoice--I shall consider that I have done you the greatest service
which it was in my power to do--if I have thus convinced you that the
great question which we have been discussing is not one to be dealt with
by rhetorical flourishes, or by loose and superficial talk; but that it
requires the keen attention of the trained intellect and the patience of
the accurate observer.

ON THE PHYSICAL BASIS OF LIFE

[1868]

In order to make the title of this discourse generally intelligible, I
have translated the term "Protoplasm," which is the scientific name of
the substance of which I am about to speak, by the words "the physical
basis of life." I suppose that, to many, the idea that there is such a
thing as a physical basis, or matter, of life may be novel--so widely
spread is the conception of life as a something which works through
matter, but is independent of it; and even those who are aware that
matter and life are inseparably connected, may not be prepared for the
conclusion plainly suggested by the phrase, "_the_ physical basis or
matter of life," that there is some one kind of matter which is common
to all living beings, and that their endless diversities are bound
together by a physical, as well as an ideal, unity. In fact, when first
apprehended, such a doctrine as this appears almost shocking to common
sense.

What, truly, can seem to be more o