138 THE ROYAL SOCIETY OF CANADA 
now consistently publish a revised account with the necessary alteration 
and say, “These are the facts to-day.” The original facts have not 
changed since yesterday. If, however, in publishing his narrative 
yesterday he professed to say only, “This is what is worthy of belief,” 
he may now with consistency make the necessary change and say, 
“This is what is worthy of belief to-day.” By the discovery of the new 
evidence what was worthy of belief yesterday has been changed to-day. 
The historian thus in dealing with the facts of the past does so 
purely from a present stand-point and through an existing medium. 
In determining what is worthy of belief concerning an event he is not 
answerable for information which was available a day, a year or a 
century ago, if in the interval by loss of records or otherwise the evidence 
supplying this information has passed beyond his reach. Neither is he 
accountable for information which may be available a day, a year or a 
century hence if the records or other sources of such information, though 
in existence, have not yet come to light. A certain amount of evidence 
is in existence and available now. On this evidence and on it alone he 
can base his conclusions. The records and other media through which 
this evidence is supplied, though dealing with past events, are as strictly 
present materials and the historian’s problems in dealing with them are 
as strictly present problems as are the materials and problems which 
face the chemist in the laboratory, the mathematician in his study or 
the engineer in the field. And the historian, in so far as he purposes to 
be a man of science, must deal with his materials and solve his 
problems with the same obedience to fundamental scientific principles 
as is required of the chemist, of the mathematician, of the engineer, or 
of any student or operator in any other field of theoretical or practical 
science. An historian fulfilling this requirement may be subject still 
to incidental error. His work none the less will be essentially trust- 
worthy. By additions of evidence his results may be greatly amplified 
and extended, or incidental errors disclosed. His conclusions as a whole 
or in essentials can never be overthrown. 
II. FUNDAMENTAL PRINCIPLES OF SCIENCE. 
In order to reach and preserve correct conclusions and results in the 
scientific investigation and solution of problems, theoretical or practical, 
the following four principles are necessary and may be termed funda- 
