36 THE GROUNDWORK OF SCIENCE

as for example an apple, what are really its various qualities ?

Are they not rather ours than the apple's? We think that

we look at it, but all we see is a definitely shaped patch of

colour, and that is a sensation of our own. We take it up

and hold it to the nose, when we perceive its apple-odour.

But that is only another of our sensations. We may grasp it,

feel it, and squeeze it, and these acts will occasion a number

of other sensations through our skin, muscles and the nerves

supplying both, and these sensations are merely our own

feelings once more, though we refer them to an imagined

object and say that it is rounded and rather hard. We may

tap it on a table or drop it on the ground, when we shall hear

sounds ; in other words, we shall experience sensations of

another order. Finally, we may bite it, and so have other

experiences of resistance overcome and a pleasant flavour ;

but the taste is certainly not in the apple, but in us. It is but

one mental state the more. Do what we may we cannot by

examining any so-called material object arrive at anything

more than modifications of our own mental states different

feelings. Other feelings we have, indeed, of a less vivid kind.

These, however, are nothing but faint revivals of sensations

previously experienced, or of feelings of the modes in which

such previously experienced feelings have stood one to

another. Such ' faint revivals ' and ' faint feelings of modes

of sensation ' we call ' ideas.' These vivid and faint feelings

are the only things which can be perceived by us, and the

whole of our knowledge consists of nothing else. Therefore,

as far as we know, nothing exists or can exist except as

something felt and perceived. We cannot even conceive

anything otherwise existing, and therefore the very essence of

'existence' must consist in being perceived. Evidently an

' idea ' or a ' sensation ' can be like nothing but an idea or a

sensation. A colour, taste, smell, or sound can be like nothing

but a colour, taste smell, or sound. We can have no

as for example an apple, what are really its various qualities ?

Are they not rather ours than the apple's? We think that

we look at it, but all we see is a definitely shaped patch of

colour, and that is a sensation of our own. We take it up

and hold it to the nose, when we perceive its apple-odour.

But that is only another of our sensations. We may grasp it,

feel it, and squeeze it, and these acts will occasion a number

of other sensations through our skin, muscles and the nerves

supplying both, and these sensations are merely our own

feelings once more, though we refer them to an imagined

object and say that it is rounded and rather hard. We may

tap it on a table or drop it on the ground, when we shall hear

sounds ; in other words, we shall experience sensations of

another order. Finally, we may bite it, and so have other

experiences of resistance overcome and a pleasant flavour ;

but the taste is certainly not in the apple, but in us. It is but

one mental state the more. Do what we may we cannot by

examining any so-called material object arrive at anything

more than modifications of our own mental states different

feelings. Other feelings we have, indeed, of a less vivid kind.

These, however, are nothing but faint revivals of sensations

previously experienced, or of feelings of the modes in which

such previously experienced feelings have stood one to

another. Such ' faint revivals ' and ' faint feelings of modes

of sensation ' we call ' ideas.' These vivid and faint feelings

are the only things which can be perceived by us, and the

whole of our knowledge consists of nothing else. Therefore,

as far as we know, nothing exists or can exist except as

something felt and perceived. We cannot even conceive

anything otherwise existing, and therefore the very essence of

'existence' must consist in being perceived. Evidently an

' idea ' or a ' sensation ' can be like nothing but an idea or a

sensation. A colour, taste, smell, or sound can be like nothing

but a colour, taste smell, or sound. We can have no