On Generation and corruption   

in general why the active thing assimilates to itself the patient. For

agent and patient are contrary to one another, and coming-to-be is a

process into the contrary: hence the patient must change into the

agent, since it is only thus that coming-to be will be a process

into the contrary. And, again, it is intelligible that the advocates

of both views, although their theories are not the same, are yet in

contact with the nature of the facts. For sometimes we speak of the

substratum as suffering action (e.g. of 'the man' as being healed,

being warmed and chilled, and similarly in all the other cases), but

at other times we say 'what is cold is 'being warmed', 'what is sick

is being healed': and in both these ways of speaking we express the

truth, since in one sense it is the 'matter', while in another sense

it is the 'contrary', which suffers action. (We make the same

distinction in speaking of the agent: for sometimes we say that 'the

man', but at other times that 'what is hot', produces heat.) Now the

one group of thinkers supposed that agent and patient must possess

something identical, because they fastened their attention on the

substratum: while the other group maintained the opposite because

their attention was concentrated on the 'contraries'. We must conceive

the same account to hold of action and passion as that which is true

of 'being moved' and 'imparting motion'. For the 'mover', like the

'agent', has two meanings. Both (a) that which contains the

originative source of the motion is thought to 'impart motion' (for

the originative source is first amongst the causes), and also (b) that

which is last, i.e. immediately next to the moved thing and to the

coming-to-be. A similar distinction holds also of the agent: for we

speak not only (a) of the doctor, but also (b) of the wine, as

healing. Now, in motion, there is nothing to prevent the firs; mover

being unmoved (indeed, as regards some 'first' movers' this is

actually necessary) although the last mover always imparts motion by

being itself moved: and, in action, there is nothing to prevent the

first agent being unaffected, while the last agent only acts by