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subject in which they naturally subsist, or of which they are

predicated; for it is those, as we proved,' in the case of which

this necessity obtains, that have no intermediate. Moreover, we

cited health and disease, odd and even, as instances. But those

contraries which have an intermediate are not subject to any such

necessity. It is not necessary that every substance, receptive of such

qualities, should be either black or white, cold or hot, for something

intermediate between these contraries may very well be present in

the subject. We proved, moreover, that those contraries have an

intermediate in the case of which the said necessity does not

obtain. Yet when one of the two contraries is a constitutive

property of the subject, as it is a constitutive property of fire to

be hot, of snow to be white, it is necessary determinately that one of

the two contraries, not one or the other, should be present in the

subject; for fire cannot be cold, or snow black. Thus, it is not the

case here that one of the two must needs be present in every subject

receptive of these qualities, but only in that subject of which the

one forms a constitutive property. Moreover, in such cases it is one

member of the pair determinately, and not either the one or the other,

which must be present.

In the case of 'positives' and 'privatives', on the other hand,

neither of the aforesaid statements holds good. For it is not

necessary that a subject receptive of the qualities should always have

either the one or the other; that which has not yet advanced to the

state when sight is natural is not said either to be blind or to

see. Thus 'positives' and 'privatives' do not belong to that class

of contraries which consists of those which have no intermediate. On

the other hand, they do not belong either to that class which consists

of contraries which have an intermediate. For under certain conditions

it is necessary that either the one or the other should form part of

the constitution of every appropriate subject. For when a thing has

reached the stage when it is by nature capable of sight, it will be