269 
of Edinburgh^ Session 1864-65. 
iimumerable structures leave upon the mind. Take, for ex- 
ample, the word “ Contrivance.” How could science do without 
it? How could the great subject of animal mechanics be dealt 
with scientifically without continual reference to Law as that by 
which, and through which, special organs are formed for the doing 
of special work. What is the very definition of a machine ? 
Machines do not increase force, they only adjust it. The very 
idea and essence of a machine is that it is a contrivance for the 
distribution of force with a view to its bearing on special purposes. 
A man’s arm is a machine in which the law of leverage is supplied 
by the vital force for the purposes of prehension. A bird’s wing is 
a machine in which the same law is supplied, under most com- 
plicated conditions, for the purposes of flight. It is impossible to 
describe the facts we meet with in this or in any other branch of 
science, without investing the laws of nature with something of that 
personality which they do actually reflect, or without conceiving 
of them as partaking of those attributes of mind which we every- 
where recognise in their working and results. If any one imagines 
that the idea of Creation by Law casts out the idea of creation 
under the supreme control of purpose, let him read one of the 
later works of Mr Darwin, — I refer to his most curious work on 
“ The Fertilisation of the Orchids.” In investigating the laws 
which determine the form and the propagation of this strange 
order of plants, Mr Darwin finds it impossible to describe them 
without exhausting all the forms of language in which we can 
express the workings of intention and of mind in the determina- 
tion of physical results. 
I am afraid that to some this discussion may, at first sight, 
appear irrelevant. But I am sure this impression will be removed 
in those who recollect how powerfully ambiguity of language 
reacts upon the progress of knowledge. Words which should be 
the servants of thought are too often its masters ; and I know of 
no word which has been used more ambiguously, and therefore more 
injuriously, than the word Law.” I do not mean that it may not 
be legitimately used in several different senses. It is in all cases, 
as applied in science, a metaphor, and one which has relation to 
many different kinds and degrees of likeness in the ideas which are 
compared. It matters little in which of these senses it is used. 
