INTELLECTUAL ANTECEDENTS OF SCIENCE 245

That nothing can simultaneously be existent and non-exist-

ent does not at all depend on the words employed to denote

that truth, but is "a law of things? It would not lose its

validity and objective truth, not only if there were no such

things as "words " at all, but it would not lose them if the whole

human race came to an end. The necessity and universality

of this principle is easily recognized. Thus if we think of

what the condition of things must have been a long time ago

in the days of Julius Caesar, or when palaeolithic implements

were first fashioned we shall see that the law of contradiction

is as sure and certain with respect to the past as it is with

the present. We do not " think," we actually " know " with

absolute certainty that had Julius Caesar been drowned off

the coast of Britain he could not also have been assassinated

in the Roman Senate House, as also that at the time when

some early palaeolithic man was in the act of fashioning a

flint implement, he had not then both his hands empty. The

same certainty exists as to the most distant regions. We are

quite sure that the moon's surface cannot be both mountainous

and also absolutely smooth, and that the spectrum of a fixed

star which shows certain definite lines, cannot at the same

time be devoid of them. Such assertions might well seem too

superfluous and trivial did not men who have written letters

to the journal named Nature, make it only too evident that

they are sorely needed.

This first principle, this law, then, is one of those which

are at once both absolute and universally necessary, while

they are incapable of proof and carry with them their own

evidence.

But it is possible that one or two of our readers may be

startled at those words we have more than once used, namely,

" absolutely necessary " and " universal." They may feel

some vague doubt as to how this matter may be in the Dog-

star now, or how it may have been long ages before our

That nothing can simultaneously be existent and non-exist-

ent does not at all depend on the words employed to denote

that truth, but is "a law of things? It would not lose its

validity and objective truth, not only if there were no such

things as "words " at all, but it would not lose them if the whole

human race came to an end. The necessity and universality

of this principle is easily recognized. Thus if we think of

what the condition of things must have been a long time ago

in the days of Julius Caesar, or when palaeolithic implements

were first fashioned we shall see that the law of contradiction

is as sure and certain with respect to the past as it is with

the present. We do not " think," we actually " know " with

absolute certainty that had Julius Caesar been drowned off

the coast of Britain he could not also have been assassinated

in the Roman Senate House, as also that at the time when

some early palaeolithic man was in the act of fashioning a

flint implement, he had not then both his hands empty. The

same certainty exists as to the most distant regions. We are

quite sure that the moon's surface cannot be both mountainous

and also absolutely smooth, and that the spectrum of a fixed

star which shows certain definite lines, cannot at the same

time be devoid of them. Such assertions might well seem too

superfluous and trivial did not men who have written letters

to the journal named Nature, make it only too evident that

they are sorely needed.

This first principle, this law, then, is one of those which

are at once both absolute and universally necessary, while

they are incapable of proof and carry with them their own

evidence.

But it is possible that one or two of our readers may be

startled at those words we have more than once used, namely,

" absolutely necessary " and " universal." They may feel

some vague doubt as to how this matter may be in the Dog-

star now, or how it may have been long ages before our