3 o 4 THE GROUNDWORK OF SCIENCE

material substances co-existing beside, or within, any

moving, hot, or luminous body. The days of " phlogiston "

are at an end. But is it possible that they may each

severally be a manifestation of some immaterial constituent

of bodies ?

Every material body known to us we know through some

power or quality which we perceive it to possess, whereby

we also distinguish it from other bodies. But the active

powers which thus pervade material bodies are no more

themselves material than are motion, light, and heat.

But what is matter? It is an entity perceived intel-

lectually by the aid of our sensitivity, and constituting

those substantial objects of which our senses take cognizance.

Through our sense-perceptions the intellect acquires an

intuition, not only of extended bodies, but also of matter,

as, at least in part, composing them. Yet though matter

is thus constantly and familiarly known as existing in

bodies, pure and simple, " matter " itself remains unknown,

and has never been revealed to any man, and shows no

signs of existing in reruni natura.

What we always perceive is matter of one or another

definite kind. It is always a " sort of matter," and never

simply " matter," which we come to know. Matter seems

never to exist unmodified, though it abounds in un-

imaginable transformations of material substances of all

kinds.

Thus every material body or substance known to us

seems to consist of something corresponding with our

idea of matter, and something immaterial some energy

existing with the matter whereby that body or substance

comes to possess and exercise those active powers

which make it known to us as being whatever kind of

body or substance it may happen to be that immaterial

constituent being the active and dominant principle. But

material substances co-existing beside, or within, any

moving, hot, or luminous body. The days of " phlogiston "

are at an end. But is it possible that they may each

severally be a manifestation of some immaterial constituent

of bodies ?

Every material body known to us we know through some

power or quality which we perceive it to possess, whereby

we also distinguish it from other bodies. But the active

powers which thus pervade material bodies are no more

themselves material than are motion, light, and heat.

But what is matter? It is an entity perceived intel-

lectually by the aid of our sensitivity, and constituting

those substantial objects of which our senses take cognizance.

Through our sense-perceptions the intellect acquires an

intuition, not only of extended bodies, but also of matter,

as, at least in part, composing them. Yet though matter

is thus constantly and familiarly known as existing in

bodies, pure and simple, " matter " itself remains unknown,

and has never been revealed to any man, and shows no

signs of existing in reruni natura.

What we always perceive is matter of one or another

definite kind. It is always a " sort of matter," and never

simply " matter," which we come to know. Matter seems

never to exist unmodified, though it abounds in un-

imaginable transformations of material substances of all

kinds.

Thus every material body or substance known to us

seems to consist of something corresponding with our

idea of matter, and something immaterial some energy

existing with the matter whereby that body or substance

comes to possess and exercise those active powers

which make it known to us as being whatever kind of

body or substance it may happen to be that immaterial

constituent being the active and dominant principle. But