74 THE GROUNDWORK OF SCIENCE

triangle are equal " false or erroneous, because it does not

also express the facts which follow if its sides be produced ?

Is it false to say " A gibbon has extremely long arms,"

because we do not also say " No ape except a species of

gibbon has a chin " ?

It is, of course, most true that no man can possess, with

respect to any object whatever, a knowledge of all its

relations (real and possible) with the rest of the universe.

But the impossibility of our being omniscient does not

prevent our having some knowledge which is perfectly

accurate, absolutely true, as far as it goes. Our knowledge,

for example, of the numerical difference between two groups

of marbles (one with three, -the other with five) is a perfectly

true knowledge, and in no way tainted with error.

The same example may serve to refute another and very

common objection to the veracity of our perceptions. Some

persons, while professing to know nothing but sensations and

sense-impresses, vivid and faint, yet believe as a sort of faith

in the existence of an independent material world, quite

unlike our perceptions, and yet the cause of them. The men

of this school do really believe in " independent material

objects " and "actual physical states," as realities independent

of their minds and of everyone else's. But, on their system

of knowledge, they can (since they say they can know

nothing but states of consciousness) only get this belief of

theirs by an act of blind and unreasoning credulity. They

also affirm our knowledge to be necessarily untrue, because

it corresponds neither with what is internal and subjective,

nor with what is external and objective. They regard it

as a sort of tertium quid which results from the combined

activity and interaction of both subject and object, but

resembling neither just as water resembles neither the

oxygen nor the hydrogen from the combination of both of

which it results. But experience and reflexion clearly show

triangle are equal " false or erroneous, because it does not

also express the facts which follow if its sides be produced ?

Is it false to say " A gibbon has extremely long arms,"

because we do not also say " No ape except a species of

gibbon has a chin " ?

It is, of course, most true that no man can possess, with

respect to any object whatever, a knowledge of all its

relations (real and possible) with the rest of the universe.

But the impossibility of our being omniscient does not

prevent our having some knowledge which is perfectly

accurate, absolutely true, as far as it goes. Our knowledge,

for example, of the numerical difference between two groups

of marbles (one with three, -the other with five) is a perfectly

true knowledge, and in no way tainted with error.

The same example may serve to refute another and very

common objection to the veracity of our perceptions. Some

persons, while professing to know nothing but sensations and

sense-impresses, vivid and faint, yet believe as a sort of faith

in the existence of an independent material world, quite

unlike our perceptions, and yet the cause of them. The men

of this school do really believe in " independent material

objects " and "actual physical states," as realities independent

of their minds and of everyone else's. But, on their system

of knowledge, they can (since they say they can know

nothing but states of consciousness) only get this belief of

theirs by an act of blind and unreasoning credulity. They

also affirm our knowledge to be necessarily untrue, because

it corresponds neither with what is internal and subjective,

nor with what is external and objective. They regard it

as a sort of tertium quid which results from the combined

activity and interaction of both subject and object, but

resembling neither just as water resembles neither the

oxygen nor the hydrogen from the combination of both of

which it results. But experience and reflexion clearly show