Marcu 8, 1912] 
This quotation is followed by a paragraph 
containing the following sarcastic remarks 
(p. 966) : 
It would indeed be comforting to be able to 
repose with such a spirit of confidence and con- 
tentment in a general philosophy of behavior, but 
it is perhaps pertinent to enquire if the author 
has not been deceived with the delusive appearance 
of explanation where no real explanation has been 
given. . . . Phenomena may thus be ‘‘accounted 
for’’ on the basis of varying internal states, but 
as it is admitted that in most cases we are entirely 
ignorant of what these states are we are about 
as much enlightened as we are by the celebrated 
explanation of the sleep-producing effect of opium 
by attributing it to a dormitive principle. 
If I had said nothing more than is con- 
tained in the paragraph which Holmes 
quoted from my book there might be some ex- 
cuse for such criticism, but the very sentence 
following this paragraph reads: 
But what are these physiological states and of 
what do they consist? That there are such states 
in organisms can not reasonably be doubted, and 
that the reactions are dependent upon them much 
as Jennings assumes, seems to me to have been 
well established in his work. But what regulates 
the physiological states is a question concerning 
which we have as yet but little knowledge. 
The two pages in my book following this 
quotation are devoted to an attempt to illus- 
trate the limitation of Jennings’s ideas, and it 
is concluded (p. 375): 
For all that is known to the contrary, subjective 
factors, entelechies, or psychoids, factors foreign 
to inorganics, may have a hand in controlling 
physiological changes and consequently the reac- 
tions. Such factors have been postulated by the 
vitalists and neovitalists, notably by Hans Driesch. 
I am at a loss to know how my critic could 
have read even superficially these statements 
and the argument connected with them and 
still conclude that I had been deceived with 
the delusive appearance of explanation where 
no real explanation has been given. I am 
not certain what Holmes means by a real ex- 
planation, but I am certain that neither Jen- 
nings nor I has ever even so much as inti- 
mated that the demonstration that reactions 
SCIENCE 
373 
of organisms are dependent in a definite way 
upon internal states constitutes a complete 
explanation of behavior. In the paragraph 
which Holmes singled out for attack with 
reference to this question I did not even use 
the term explanation, merely stating that the 
reactions could be “accounted for” by the 
application of certain ideas regarding internal 
states. Thus it is evident that his caustic 
criticism is directed not toward anything actu- 
ally stated, but toward an imaginary implica- 
tion. 
However, to intimate as Holmes does in the 
second quotation given above, that a demon- 
stration of the actual value of internal factors 
in behavior is useless because it is not known 
precisely what the internal factors are, is ex- 
pressing a principle which if applied generally 
would at once do away with scientific investi- 
gation, for is it not well known that science 
in all of its aspects rests upon phenomena 
which are clothed in mystery? A scientific ex- 
planation, as I see it, consists of a demonstra- 
tion of the order of events involved in the 
phenomenon. The demonstration that in the 
observed phenomena known as behavior events 
within the organism occur in a certain order 
in the whole series of events ending in these 
phenomena (behavior) is as truly an explana- 
tion as any we have in science. It is one step 
in the series, even if only a small one, which, 
as far as can be predicted at present, leads 
back into the unknown without end. 
I can understand the statements of Holmes 
in his eriticisms only on the assumption that 
he reviewed my book hurriedly and carelessly. 
As evidence of this we have not only his 
erroneous conceptions regarding Loeb’s defi- 
nition of tropism and his failure to grasp my 
ideas in the discussion of the theoretical 
views of Jennings, but also the fact that in his 
short quotation from my book there are three 
changes from the original. Moreover, his 
statement (p. 965) that I have presented “no 
discussion of any theoretical attempt to ex- 
plain the reversal of phototaxis” is not true, 
as reference to page 370 will show. 
S. O. Mast 
JOHNS HopkKINS UNIVERSITY 
