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outside the eyeball, combine the double visual spectra into 
single ones, and place in its proper position the inverted map of 
the retina. In these, therefore, as in many other instances, we 
have on the one side sense and appearance, and on the other 
side reason and reality. In these cases, there has been no hesi- 
tation amongst scientific men as to which side is to be chosen ; 
but it can hardly be said that they have invariably followed the 
guidance of the same principle of choice. Whilst recognizing 
that the senses have led men totally wrong as to the real 
sequence and nature of some of the most stupendous, and at the 
same time most familiar, phenomena of the material universe, 
they have implicitly followed the guidance of the same senses 
as regards the interpretation of other phenomena of a kindred 
nature. When overmastered by strongly-held theoretical con- 
\ictions, it is true of all men, — of men of science as of the pro- 
fane vulgar, — that “ populus vult clecipi, et decipiatur 
Leaving theoretical questions in the meanwhile for others 
more practical, it may here be pointed out that the Sciences 
are twofold in aspect and constitution, and are adapted to play 
a double part in the complicated machinery of education. The 
data of the sciences, the facts which each embraces, are learn- 
able by the senses, and are not truly or properly learnable by 
any other channel. It is possible, of course, to learn some or 
all of the known facts of a given science out of books, by 
memory alone, and without having submitted one of these facts 
to the test of the senses. It is possible to do this; but, from 
the very definition of what Science in its essence is, it must be 
evident that no real knowledge can be obtained in this fashion; 
and the Sciences, if they are to be learnt, or taught, after this 
method, assuredly present no special advantages over many 
other studies. On the other hand, the Sciences, as we have 
seen, have the peculiarity, as compared with the non-scientific 
branches of study, that they are grounded in the sensuous and 
natural life of the human being. They reach the higher 
spiritual plane of the organism through the senses, and it is 
properly through “ the five gateways of knowledge” that 
scientific truths should be imparted to the learner. Ilcncc, 
the Sciences present, to begin with, the advantage that they 
can be taught, as regards their simpler and more fundamental 
data, at a time when the higher mental faculties arc compara- 
tively undeveloped and in abeyance. Whether purposely 
taught, indeed, or not, every individual of our race, from the 
moment that lie opens his eyes upon the world, commences 
perforce such a course of scientific education, which is none the 
less complete because it is involuntary and guided only by the 
