86 
Proceedings of the Royal Society . 
matics in Queen’s College Cork, which he still holds. He com- 
menced his career as professor somewhat daringly, by publishing in 
succession,- — ls£, “A Lecture on the Claims of Science,” in which he 
advances out of his subject into the domain of mental philosophy. 2 d, 
“An Investigation of the Laws of Thought.” This last volume, which 
is equally remarkable for clearness of enunciation, breadth of gene- 
ralization, and originality, of thought, is the prelude to the paper 
for which we this day present Mr Boole with the Keith Medal. 
Mr Leslie Ellis has pointed out in the first volume of the collected 
works of Bacon, that some of the germs of Mr Boole’s ideas are to 
be found in the writings of that great philosopher, and in those 
of Leibnitz. But this, instead of detracting from the claims of Mr 
Boole, is rather a proof of his power, or at any rate of his sagacity 
in seizing on and developing ideas which lay unexpanded in the 
records of minds so vast and so original. 
This is all I shall say about the ‘person on whom the Keith Medal 
is to be conferred. 
2. Let me now very briefly refer to the paper for which this 
award has been made. The problems which the author pro- 
poses to solve are these : — That of combining testimonies whose 
different values may be regarded as numerical measures of a physi- 
cal magnitude. 2 d, The same problem in which the testimonies 
are not only expressible, as in the former, but relate to some fact 
or hypothesis of which it is sought to determine the probability. Re- 
lative to the former of these, an important element, now, I believe, 
first completely discussed, is the determination of the “ Conditions 
of Possible Experience.” Suppose, for example, it were asserted 
that of all cases of a certain disease, two-fifths of the patients were 
affected with shivering and sweating, two-thirds with shivering and 
thirst, and four-fifths with sweating and thirst, this very assertion 
would be found to contain within itself the elements of its own con- 
demnation, seeing that it violates the conditions of possibility. 
The other problem has for its object, to combine the force of two 
testimonies in support of a fact, the strength of each separate tes- 
timony being given. That a complete discussion of this problem 
is most valuable in itself cannot be doubted. What has here been 
written may rather be regarded as material for a future judgment 
than as exhausting the consideration of the question. There are 
so many conditions to be taken into account, and such a tendency 
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