252 TRANSACTIONS OF THE PLYMOUTH INSTITUTION. 
scientific knowledge are being constantly extended by actual 
observation, experiment, and due verification of both, yet it is also 
true that scientific knowledge is being extended by the application 
of principles, inductively obtained from such verified observation 
and experiment, to cases which lie beyond all observation, and in 
some instances incapable of verification. There are such things as 
universal principles, not only in the exact sciences, but also in 
natural sciences. Especially is there a probability that the 
progress of the Cosmos has been pervaded by a uniform law. It 
would seem to be the dictate of reason that the universe has been 
constructed on definite principles, so that the deductive application 
of principles inductively acquired is not only a legitimate process, 
but is the method adopted in all departments of research. It 
would be unnecessary to dwell on a point so familiar to many, were 
it not desirable, in a discussion like the present, to pave the way 
for the consideration of varying views without prejudice. 
So far, then, we are on solid ground. We may reasonably 
approach the consideration of the origin of the first germinal life, 
though, with the use of our present assured knowledge, we may not 
be sure of reaching in every case an unassailable conclusion. 
The next point to settle is the method by which it is possible 
to arrive at some conclusion, seeing that we were not there to 
make observations and apply tests when the event took place. 
Now, the actual mental process followed by those who have worked 
at the problem seems to me to have been something of this kind. 
It may be asked, first, whether there are any facts, or well- 
grounded conclusions, respecting the course of Nature — and 
especially respecting the successive changes in the upward line of 
the world's history — which may give a clue to, or serve to suggest, 
the conditions and circumstances antecedent to, and concurrent in, 
the first appearance of Life. In other words, Are we in possession 
of any scientific knowledge which points to, with any high degree 
of probability, the actual method chosen by Providence for the 
origination of Life % Then, it may be further asked, is there any- 
thing in the constitution of a living organism, as we now know it, 
which, physically considered, indicates the direction in which we 
are to look for its origin in the first instance % Can we reason 
back from what we now find to be in an organic structure to the 
formation of the simplest structure at the first ? Still further, it 
may be asked, looking at the compounds that enter into present 
