INTELLECTUAL ANTECEDENTS OF SCIENCE 227

substance in each body, constituting it essentially a " thing

in itself," belies that intuition of extension by which we know

bodies to be the self-evident entities they are, and thus and

therefore it is that Idealism is in conflict with sound sense.

So with respect to the existence of our own bodies, the

supreme certainty we have about it is not merely what is

present in the feeling of the moment, but the cognition

we have of it is gained (as we shall shortly see) through our

faculty of memory together with the exercise of reflexion.

Thus all that is most evidently and supremely certain for

us is, not as so commonly supposed, anything we experience

in sensation, nor anything we cognize in examining or

experimenting with material things, but, on the contrary,

exclusively that which is immaterial, abstract, and mental.

The truth of whatever is true, and the evidence of what-

ever is evident, can be most perfectly known only to us

by thought and not sensation. Not observation, not

experiment, not sensitivity, but thought and thought only

(as we pointed out earlier),* is and must be our supreme,

ultimate, and absolute criterion. Our last appeal in all cases

is and must ever be to a perception an intuition of the

intellect

Nevertheless, a mental world of abstract intuitions and

nothing else could never supply us with a knowledge of

science, still less with a perception of the groundwork of all

science. Abstract intuitions furnish us with fundamental

principles, which are not only priceless in themselves, but are

also indispensable elements in all reasoning. But besides

such processes of reasoning and such fundamental principles,

science requires a knowledge of absolute facts. Without

such facts all our reasonings must remain, as it were, in

the air, and could never descend to earth and become of

practical utility to us. There are, therefore, three categories

* See ante, p. 14.

substance in each body, constituting it essentially a " thing

in itself," belies that intuition of extension by which we know

bodies to be the self-evident entities they are, and thus and

therefore it is that Idealism is in conflict with sound sense.

So with respect to the existence of our own bodies, the

supreme certainty we have about it is not merely what is

present in the feeling of the moment, but the cognition

we have of it is gained (as we shall shortly see) through our

faculty of memory together with the exercise of reflexion.

Thus all that is most evidently and supremely certain for

us is, not as so commonly supposed, anything we experience

in sensation, nor anything we cognize in examining or

experimenting with material things, but, on the contrary,

exclusively that which is immaterial, abstract, and mental.

The truth of whatever is true, and the evidence of what-

ever is evident, can be most perfectly known only to us

by thought and not sensation. Not observation, not

experiment, not sensitivity, but thought and thought only

(as we pointed out earlier),* is and must be our supreme,

ultimate, and absolute criterion. Our last appeal in all cases

is and must ever be to a perception an intuition of the

intellect

Nevertheless, a mental world of abstract intuitions and

nothing else could never supply us with a knowledge of

science, still less with a perception of the groundwork of all

science. Abstract intuitions furnish us with fundamental

principles, which are not only priceless in themselves, but are

also indispensable elements in all reasoning. But besides

such processes of reasoning and such fundamental principles,

science requires a knowledge of absolute facts. Without

such facts all our reasonings must remain, as it were, in

the air, and could never descend to earth and become of

practical utility to us. There are, therefore, three categories

* See ante, p. 14.