72 7 HE GROUNDWORK OF SCIENCE

unconscious of it, save for jolts, jars, the feeling of meeting the

air, and other incidents which are no elements of motion, but

merely its accidental accompaniments. When travellers in a

balloon ascend from the earth, they are said to have no feeling

whatever of their movement, save by looking down on an

apparently sinking world beneath them. The feelings our

senses give us, occasion an intellectual apprehension of motion

and of moving things ; but that apprehension, we can see by

reflexion, may take place with or without inference. With

regard to the movement of the sun, there really is this relative

change of position a fact about which the senses give us

accurate information. Our perception of this relative change

of place does certainly awaken in our intellect a perception of

motion, but it does not, for it cannot, tell us where the motion

is, without processes of observation and inference. The

supposed perception of the sun's motion is an instance of

an inference, not noticed, perhaps, at the time, but clearly

recognizable by reflexion. It is impossible for anyone to

really see the sun move. If we fix our eyes on it at

sunset we shall, indeed, from second to second, see that it

has more and more disappeared ; but we cannot see it

move. As to the movement of the sun, the mass of men

never think about its relation to that of the earth. The first

observers inferred that it moved, and that the earth stood still,

and their inference, embedded in language, has so affected us,

that to this day everyone speaks of the " rising and setting

sun/' even though he may know quite well that it neither

sets nor rises, but that the revolving earth gradually hides

it from view and afterwards lets it be seen once more.

What men's senses ever did, and do now, make known, are

" changes of relative position between the earth, on which the

observer stands, and the sun," and just such changes do really

take place. Thus none of the objections yet considered

allow us to say that our senses really deceive us :

unconscious of it, save for jolts, jars, the feeling of meeting the

air, and other incidents which are no elements of motion, but

merely its accidental accompaniments. When travellers in a

balloon ascend from the earth, they are said to have no feeling

whatever of their movement, save by looking down on an

apparently sinking world beneath them. The feelings our

senses give us, occasion an intellectual apprehension of motion

and of moving things ; but that apprehension, we can see by

reflexion, may take place with or without inference. With

regard to the movement of the sun, there really is this relative

change of position a fact about which the senses give us

accurate information. Our perception of this relative change

of place does certainly awaken in our intellect a perception of

motion, but it does not, for it cannot, tell us where the motion

is, without processes of observation and inference. The

supposed perception of the sun's motion is an instance of

an inference, not noticed, perhaps, at the time, but clearly

recognizable by reflexion. It is impossible for anyone to

really see the sun move. If we fix our eyes on it at

sunset we shall, indeed, from second to second, see that it

has more and more disappeared ; but we cannot see it

move. As to the movement of the sun, the mass of men

never think about its relation to that of the earth. The first

observers inferred that it moved, and that the earth stood still,

and their inference, embedded in language, has so affected us,

that to this day everyone speaks of the " rising and setting

sun/' even though he may know quite well that it neither

sets nor rises, but that the revolving earth gradually hides

it from view and afterwards lets it be seen once more.

What men's senses ever did, and do now, make known, are

" changes of relative position between the earth, on which the

observer stands, and the sun," and just such changes do really

take place. Thus none of the objections yet considered

allow us to say that our senses really deceive us :