On Generation and corruption   

'body.' Yet this too is impossible. For our account of growth must

preserve the characteristics of that which is growing and diminishing.

And these characteristics are three: (i) any and every part of the

growing magnitude is made bigger (e.g. if flesh grows, every

particle of the flesh gets bigger), (ii) by the accession of

something, and (iii) in such a way that the growing thing is preserved

and persists. For whereas a thing does not persist in the processes of

unqualified coming-to-be or passing-away, that which grows or 'alters'

persists in its identity through the 'altering' and through the

growing or diminishing, though the quality (in 'alteration') and the

size (in growth) do not remain the same. Now if the generation of

air from water is to be regarded as growth, a thing might grow without

the accession (and without the persistence) of anything, and

diminish without the departure of anything-and that which grows need

not persist. But this characteristic must be preserved: for the growth

we are discussing has been assumed to be thus characterized.

One might raise a further difficulty. What is 'that which grows'? Is

it that to which something is added? If, e.g. a man grows in his shin,

is it the shin which is greater-but not that 'whereby' he grows,

viz. not the food? Then why have not both 'grown'? For when A is added

to B, both A and B are greater, as when you mix wine with water; for

each ingredient is alike increased in volume. Perhaps the

explanation is that the substance of the one remains unchanged, but

the substance of the other (viz. of the food) does not. For indeed,

even in the mixture of wine and water, it is the prevailing ingredient

which is said to have increased in volume. We say, e.g. that the

wine has increased, because the whole mixture acts as wine but not

as water. A similar principle applies also to 'alteration'. Flesh is

said to have been 'altered' if, while its character and substance

remain, some one of its essential properties, which was not there

before, now qualifies it: on the other hand, that 'whereby' it has

been 'altered' may have undergone no change, though sometimes it too