15 
12. Recurring to Boole, we find him (at p.p. 417-418) 
saying that it may be that the progress of natural knowledge 
tends towards the recognition of some central TJnity in Nature. 
Of such unity as consists in the mutual relation of the parts of 
a system there can be little doubt, and able men have speculated, 
not without grounds, on a more intimate correlation of physical 
forces than the mere idea of a system would lead us to con- 
jecture. Further, it may be that in the bosom of that supposed 
unity are involved some general principles of division and re- 
union, the sources, under the Supreme Will, .of much of the 
related variety of Nature. The instance of sex and polarity 
have been adduced in support of such a view. As a supposition, 
continues Boole, it is not very improbable that, in some such way 
as this, the constitution of things without may correspond to that 
of the mind within. But such correspondence, he says, if it 
shall ever be proved to exist, will appear as the last induction 
from human knowledge, not as the first principle of scientific 
inquiry ; adding, that the natural order of discovery is from the 
particular to the universal, and that it may confidently be 
affirmed that we have not yet advanced sufficiently far on this 
track to enable us to determine what are the ultimate forms into 
which all the special differences of Nature shall merge, and from 
which they shall receive their explanation. 
13. I think that the last remark deserves serious attention 
even now, and that the progress of what is called Philosophy has 
not, during the last twenty or more years, been so marked as that 
of Science. The authority of consciousness was not more fully 
recognised by Boole than by Aristotle, in whose philosophy the 
presumption in its favour obtained the authority of a principle. 
“ What appears to all , ” says Aristotle, “ that we affirm to be y and 
he who rejects this belief will, assuredly, advance nothing better 
worthy of credit.” And “If we know and believe,” says 
Aristotle, “ through Certain original principles, we must know 
and believe these with paramount certainty , for the very reason 
that we know and believe all else through them ; ”* and he else- 
where observes, that our approbation is often rather to be 
accorded to what is revealed by nature as actual, than to what 
can be demonstrated by philosophy as possible. It may be 
remarked, says Brown, f of the demonstrations of reasoning that, 
in addition to the general principle that determines to the belief 
of the agreement of the separate propositions, there is always 
some primary proposition, of which the truth is as much assumed 
as that of causation, which serves as the basis of the propositions 
that follow ; and without the assumption of the truth of which, 
as independent of the argument that follows it, there must 
either be an infinite series of propositions, or no belief whatever. 
* See Hamilton, Discussions, p. 90. The italics in the above quotations 
are his. 
t Brown, Inquiry into the Relation of Cause and Effect, third edition, 
1818, p. 475. 
