i879-] 
The Course of Nature . 
65 
actually believed in by the large majority of educated men 
at the present time ; but the confusion of thought on this 
subject, to which I have just alluded, is so great that — al- 
though I may combat no opinions actually held — it may be 
necessary to greatly modify their application, and to criticise 
the forms in which they have found expression. 
The key-note of my discourse is found in a proposition 
which is fundamental in the history of modern science, and 
without a clear understanding of which everything I say 
may be entirely misunderstood. This proposition is, that 
Science concerns itself only with phenomena and the rela- 
tions which connect them, and does not take account of any 
questions which do not in some way admit of being brought 
to the test of observation. The only universe it knows is 
that made known by the telescope, the microscope, and 
other appliances of observation. That this is the whole 
universe we should all be very sorry to suppose, and none 
more so than he who has the honour to address you. But, 
should I pretend to a scientific knowledge of what lies 
behind this visible frame, I should be adding the part of the 
rash speculator rather than of the cautious thinker. Only 
into a single field of thought do I dare to venture. When 
we trace the efforts of men to penetrate the secrets of 
Nature, we find them clearly divisible into two classes — 
philosophic speculation and scientific investigation. We 
find the objects of thought equally divisible into two classes 
— phenomena and their hidden causes, those unknowable 
entities out of which they proceed. The great progress 
which the last three centuries have witnessed has been 
wholly in the field of phenomena, and it is to this field, and 
to the results of scientific investigation in it, to which I ask 
your attention this evening. But, it is to be expended that, 
in this brief characterisation of our field of thought, I have 
failed to convey to your minds any clear conception of its 
boundaries. The progress here alluded to has been rendered 
possible only by entirely rejecting the mode of thinking 
about nature which was prevalent in former ages, and into 
which the untrained mind is almost sure to fall at the 
present day. The distinction will be evident to one mind at 
a glance, while another may be unable to comprehend it 
after all the explanations which it is possible to give. As 
my whole discourse will be misleading unless all my hearers 
have a clear conception of it, I shall endeavour to present 
you with the materials of such a conception, rather in the 
form of concrete illustrations in familiar language, than in 
that of abstract general definitions. 
VOL. ix. (n.s.) 
f 
