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Proceedings of the Royal Society of Edinburgh. [Sess. 
systematize the formation of letters into words that formed the contents of a book. 
Were he to begin by saying that he had discovered a ce7'tain word which would serve 
as a type , and from which by substitution and double decomposition all the others are 
to be derived , — that he by this means not only could form new words, but new 
books, and books almost ad infinitum , — that this word also formed an admirable 
point of comparison with all the others, — that in all this there were only a few 
difficulties, but that these might be ingeniously overcome, — he would state certainly 
an empirical truth. At the same time, however, his method would, judged by the 
light of common sense, be an absurdity. But a principle which common sense 
brands with absurdity, is philosophically false and a scientific blunder. 
Suppose the book that had formed the basis of this system were a German one, 
where all the words were found to be composed at least of two letters, still even in 
this language the viewing and systematizing of words as a series of double decom- 
positions would be no less ridiculous. 
The sure and invincible method of arriving at every truth which the mind is 
capable of discovering is always one and the same. It is that, namely, of throwing 
away all generalization, of going back to first principles, and of letting the mind be 
guided by these alone. It is the same in common matters. It is the same in 
science. To reach the structure of words we must go back, seek out the unde- 
composable elements, viz., the letters, and study carefully their powers and bearing. 
Having ascertained these, the composition and structure of every possible word is 
revealed. It would be well to call to recollection the parallelism of chemical 
research with that of every other search after truth ; for it has been in overlooking 
this, that in chemistry false and vacillating theories have been advocated and a 
wrong route so often pursued. In mathematics the starting-point is not generaliza- 
tions, but axioms, ultimate principles. In metaphysics, Descartes led the way of 
progress by analysing till he thought he could reach some ultimate elements beyond 
which it was impossible for him to go, then studying their force and power, and 
proceeding synthetically. The recognition of this method wrought the regeneration 
of science and philosophy. 
On the other hand, look where Gerhardt’s generalization of Williamson’s 
generalization leads him, and legitimately too, — a fact which his logical spirit 
clearly discerned. He is led not to explain bodies according to their composition 
and inherent properties, but to think it necessary to restrict chemical science to the 
arrangement of bodies according to their decomposition, and to deny the possibility 
of our comprehending their molecular constitution. Can such a view tend to the 
advancement of science ? Would it not be only rational, in accepting this veto, to 
renounce chemical research altogether 'l 
These reflections naturally lead to the inquiry after another theory more adequate 
to satisfy the just demands which can be made upon it. There is one which, as it 
is still supported by many distinguished chemists, cannot be passed over altogether 
unnoticed. It is that of the theory of certain combinates in organic chemistry 
which are to be viewed as analogous to, “playing the part of,” inorganic elements. 
These are denominated radicals, and are supposed to be contained in all organic 
chemical products. 
In addition to this, and also in connexion with it, there is a doctrine describing 
many combinates to be copulated, conjugated, by addition. 
