uction to his "Descent of Man,"
"Ignorance more frequently begets confidence than does knowledge: it
is those who know little and not those who know much who so positively
assert that this or that problem will never be solved by science." As
far as concerns the two separate limits which Du Bois-Reymond fixes
for human knowledge, in my opinion they are undoubtedly identical. The
problem of the origin and nature of consciousness is only a special
case of the general problem of the connection of matter and force. Du
Bois-Reymond himself indicates that this is possible at the close of
his paper; for he says, "Finally, the question arises whether the two
limitations to our natural knowledge may not perhaps be identical;
that is to say, whether if we could conceive of the true essence of
matter and force, we should not also understand how the substance
which lies at their root can, under certain given conditions, feel,
desire, and think. This conception is, no doubt, the simplest, and
according to admitted principles of inquiry it is to be preferred to
that other which it confutes, and according to which, as has been
said, the world appears doubly incomprehensible. But it is in the very
nature of things that we cannot on this point come to any clear
conclusion, and all further words on the subject are idle--and so,
'Ignorabimus.'"

The light way in which Du Bois-Reymond here passes over the most
important part of his subject is truly surprising; as if it were
ultimately indifferent whether we have before us one single insoluble
fundamental problem or two quite different ones; and as if mature
reflection did not lead to the conviction that, in fact, the second
problem is only a special case of the first general problem. I, for my
part, cannot conceive of them in any other relation; I think, too,
that all further words are by no means superfluous, but on the
contrary conduce to a very strong conviction of the unity of the
problem. That Du Bois-Reymond also has not come to any clear
conclusion on this point lies, not alone in the "nature of things,"
but, as in Virchow's case, in the nature of the investigator himself;
in his lack of knowledge of the history of evolution, and in his
neglect of those comparative and genetic methods of study, without
which, in my opinion, not even an approximate solution of this highest
and most difficult question is to be looked for.

Nothing appears to me to be of more importance for the mechan