68 THE GROUNDWORK OF SCIENCE

the idea is a plexus of feelings any more than that " coal " is

"digging" because we may have to dig in order to obtain

it. The nature of an idea and the modes of its elicitation or

acquisition are two very different things.

Our idea of " force " again becomes known to us by means

of our sense of effort, of resistance, and of resistance overcome,

and such sensations form the occasion through and by which

our intellect comes to perceive that surrounding bodies have

powers corresponding to our own. Some persons pretend

that we thus commit the absurd mistake of attributing to

inanimate bodies around us activities absolutely like our own.

But, in fact, we only attribute to such bodies powers which

have a certain analogy with our own. If we try to pull a

man up from the ground and fail because he is stronger than

we are, and if we try to raise a piece of rock and fail because

it is too heavy, we can indeed perceive a certain analogy

between the effect on us of the man and the rock, but the

difference between the two cases is also plainly evident to

the intellect, however alike may be our sensations in the two

cases. Similarly with respect to our ideas of "number,"

" extension," etc. By means of our sensations, and the

relations between them, we arrive at something funda-

mentally different from either namely, an apprehension of

external objective conditions of real independent bodies.

But, as we have said before, these conditions are utterly

unlike the sensations and relations between sensations which

serve to make such objective conditions known to us. In

considering these things we must never fail to recollect* that

it is not " sense " but " intellect," not our " feelings " but our

" perceptions," which are our ultimate criteria of certainty

and truth.

And our intellect surely tells us that by means of our

sensations we attain to a certain degree of truth with respect

* See ante, pp. 14, 15.

the idea is a plexus of feelings any more than that " coal " is

"digging" because we may have to dig in order to obtain

it. The nature of an idea and the modes of its elicitation or

acquisition are two very different things.

Our idea of " force " again becomes known to us by means

of our sense of effort, of resistance, and of resistance overcome,

and such sensations form the occasion through and by which

our intellect comes to perceive that surrounding bodies have

powers corresponding to our own. Some persons pretend

that we thus commit the absurd mistake of attributing to

inanimate bodies around us activities absolutely like our own.

But, in fact, we only attribute to such bodies powers which

have a certain analogy with our own. If we try to pull a

man up from the ground and fail because he is stronger than

we are, and if we try to raise a piece of rock and fail because

it is too heavy, we can indeed perceive a certain analogy

between the effect on us of the man and the rock, but the

difference between the two cases is also plainly evident to

the intellect, however alike may be our sensations in the two

cases. Similarly with respect to our ideas of "number,"

" extension," etc. By means of our sensations, and the

relations between them, we arrive at something funda-

mentally different from either namely, an apprehension of

external objective conditions of real independent bodies.

But, as we have said before, these conditions are utterly

unlike the sensations and relations between sensations which

serve to make such objective conditions known to us. In

considering these things we must never fail to recollect* that

it is not " sense " but " intellect," not our " feelings " but our

" perceptions," which are our ultimate criteria of certainty

and truth.

And our intellect surely tells us that by means of our

sensations we attain to a certain degree of truth with respect

* See ante, pp. 14, 15.