474 
NATURE 
[SEPTEMBER 14, 1899 
Another illustration of the illegitimate use of our hypothesis, 
as it appears to me, is in the attempt to find in the ether a fixed 
datum for the measurement of material velocities and acceler- 
ations, a something in which we can draw our coordinate axes 
so that they will never turn or bend. But this is as if, dis- 
contented with the movement of the earth’s pole, we should 
seek to find our zero lines of latitude and longitude in the 
Atlantic Ocean. Leaving out of sight the possibility of 
ethereal currents which we cannot detect, and the motions due 
to every ray of light which traverses space, we could only fix 
positions and directions in the ether by buoying them with 
matter. We know nothing of the ether, except by its effects 
on matter, and, after all, it would be the material buoys which 
would fix the positions and not the ether in which they float. 
The discussion of the physical method, with its descriptive 
laws and explanations, and its hypothetical extension of 
description, leads us on to the consideration of the limitation of 
its range. The method was developed in the study of matter 
which we describe as non-living, and with non-living matter the 
method has sufficed for the particular purposes of the physicist. 
Of course only a little corner of the universe has been explored, 
but in the study of non-living matter we have come to no 
impassable gulfs, no chasms across which we cannot throw 
bridges of hypothesis. Does the method equally suffice when 
it is applied to living matter? Can we give a purely physical 
account of such matter, likening its motions and changes to other 
motions and changes already observed, and so explaining them ? 
Can we group them in laws which will enable us to predict 
future conditions and positions? The ancient question never 
answered, but never ceasing to press for an answer. 
Having faith in our descriptive method, let us use it to 
describe our real attitude on the question. Do we, or do we 
not, as a matter of fact, make any attempt to apply the physical 
method to describe and explain those motions of matter which 
on the psychical view we term voluntary ? 
Any commonplace example, and the more commonplace the 
more is it to the point, will at once tell us our practice, 
whatever may be our theory, For instance, a steamer is 
going across the Channel. We can give a fairly good physical 
account of the motion of the steamer. We can describe 
how the energy stored in the coal passes out through the boiler 
into the machinery, and how it is ultimately absorbed by the 
sea. And the machinery once started, we can give an account 
of the actions and reactions between its various parts and the 
water, and if only the crew will not interfere, we can predict 
with some approach to correctness how the vessel will run. All 
these processes can be likened to processes already studied— 
perhaps on another scale—in our laboratories, and from the 
similarities prediction is possible. But now think of a passenger 
on board who has received an invitation to take the journey. 
It is simply a matter of fact that we make no attempt at a com- 
plete physical account and explanation of those actions which 
he takes to accomplish his purpose. We trace no lines of in- 
duction in the ether connecting him with his friends acrcss the 
Channel, we seek no law of force under which he moves. In 
practice the strictest physicist abandons the physical view, and 
replaces it by the psychical. He admits the study of purpose 
as well as the study of motion. 
He has to admit that here his physical method of prediction 
fails. In physical observations one set of measurements may 
lead to the prediction of the results of another set of measure- 
ments. The equations expressing the laws imply different ob- 
servations with some definite relation between their results, and 
if we know one set of observations and that definite relation 
we can predict the result of the other set. But if we take the 
psychical view of actions, we can only measure the actions. We 
have no independent means of studying and measuring the 
motions which preceded the actions, we can ‘only estimate their 
value by the consequent actions. If we formed equations, they 
would be mere identities with the same terms on either side. 
The consistent and persistent physicist, finding the door 
closed against him, finding that he has hardly a sphere of in- 
fluence left to him in the psychical region, seeks to apply his 
methods in another way by assuming that if he knew all about 
the molecular positions and motions in the living matter, then 
the ordinary physical laws could be applied and the physical 
of measurement much more ancient and still far more extensively used 
—the measurement by weight supported. Each method has its own range; 
each is fundamental in that range. It is one of the great practical problems 
n physics to make the pendulum give us the exact ratio of the units in the 
Wo systems. 
NO. 1559, VOL. 60] 
conditions at any future time could be predicted. He would 
say, I suppose, with regard to the Channel passenger, that it is 
absurd to begin with the most complicated mechanism, and 
seek to give a physical account of that. He would urge that 
we should take some lower form of life where the structure and 
motions are simpler, and apply the physical methods to that. 
Well, then, let us look for the physical explanation of any 
motion which we are entitled from its likeness to our own 
action to call a voluntary motion. Must we not own that even 
the very beginning of such explanation is as yet non-existent ? 
It appears to me that the assumption that our methods do apply, 
and that purely physical explanation will suffice to predict all 
motions and changes, voluntary and involuntary, is at present 
simply a gigantic extra-polation, which we should unhesitatingly 
reject if it were merely a case of ordinary physical investigation. 
The physicist when thus extending his range is ceasing to be a 
physicist, ceasing to be content with his descriptive methods in 
his intense desire to show that he is a physicist throughout. 
Of course we may describe the motions and changes of any 
type of matter after the event, and in a purely physical 
manner. And as Prof. Ward has suggested, in a most im- 
portant contribution to this subject which he has made in his 
recently published ‘‘ Gifford Lectures” (‘‘ Naturalism and 
Agnosticism,” Zhe Gifford Lectures, 1896-98, vol. ii. p. 71), 
where ordinary physical explanations fail to give an 
account of the motions, we might imagine some structure in the 
ether, and such stresses between the ether and matter that our 
physical explanations should still hold. But, as Prof. Ward 
says, such ethereal constructions would present no warrant for 
their reality or consistency. Indeed they would be mere images 
in the surface of things to account for what goes on in front of 
the surface, and would have no more reality than the images of 
objects in a glass. 
If we have full confidence in the descriptive method, as ap- 
plied to living and non-living matter, it appears to me that up to 
the present it teaches us that while in non-living matter we can 
always find similarities, that, while each event is like other 
events, actual or imagined, in a living being there are always 
dissimilarities. Taking the psychical view—the only view which 
we really do at present take—in the living being there is always 
some individuality, something different from any other living 
being, and full prediction in the physical sense, and by physical 
methods, is impossible. If this be true, the loom of nature is 
weaving a pattern with no mere geometrical design, The 
threads of life, coming in we know not where, now twining 
together, now dividing, are weaving patterns of their own, ever 
increasing in intricacy, ever gaining in beauty. 
5 Ei CaO uN, B: 
CHEMISTRY. 
OPENING ApbDREss BY Dr. Horace T. Brown, F.R.S., 
PRESIDENT OF THE SECTION. 
THE subject which I have chosen for my Address is the 
fixation of carbon by plants, one which is the common 
meeting ground of chemistry, physics and biology. I must, 
however, confine myself only to certain aspects of the question, 
since it is manifestly impossible to fully discuss the whole of a 
subject of such magnitude and importance within the time at my 
disposal. 
We have become so accustomed to the idea that the higher 
plants derive ¢4e whole of their carbon from atmospheric sources 
that we are apt to forget how very indirect is the nature of 
much of the experimental evidence on which this belief is 
founded. There can, of course, be no doubt that the primary 
source of the organic carbon of the soil, and of the plants grow- 
ing on it, is the atmosphere; but of late years there has been 
such an accumulation of evidence tending to show that the 
higher plants are capable of being nourished by the direct ap- 
plication of a great variety of ready-formed organic compounds, 
that we are justified in demanding further proof that the stores 
of organic substances in the soil must necessarily be oxidised 
down to the lowest possible point before their carbon is once 
more in a fit state to be assimilated. 
It was the hope of gaining more direct evidence on this im- 
portant question which led me some time ago to attack the 
problem experimentally in conjunction with Mr. F. Escombe, 
the resources of the Jodrell Laboratory at Kew having been 
