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＇the weakness of our＇ sense； are imperceptible by us； but a mixture by
which they ＇i。e。 the 'matter' of which they consist＇ are wholly
blent together by interpenetration； as we have described it in the
treatise on Mixture； where we dealt with this subject generally in its
most comprehensive aspect。 For； on the supposition we are criticizing；
the only totals capable of being mixed are those which are divisible
into minimal parts； ＇e。g。 genera into individuals＇ as men； horses；
or the ＇various kinds of＇ seeds。 For of mankind as a whole the
individual man is such a least part； of horses ＇as an aggregate＇ the
individual horse。 Hence by the juxtaposition of these we obtain a
mixed total； consisting ＇like a troop of cavalry＇ of both together；
but we do not say that by such a process any individual man has been
mixed with any individual horse。 Not in this way； but by complete
interpenetration ＇of their matter＇； must we conceive those things to
be mixed which are not divisible into minima； and it is in the case of
these that natural mixture exhibits itself in its most perfect form。
We have explained already in our discourse 'On Mixture' how such
mixture is possible。 This being the true nature of mixture； it is
plain that when bodies are mixed their colours also are necessarily
mixed at the same time； and ＇it is no less plain＇ that this is the
real cause determining the existence of a plurality of colours… not
superposition or juxtaposition。 For when bodies are thus mixed；
their resultant colour presents itself as one and the same at all
distances alike； not varying as it is seen nearer or farther away。
Colours will thus； too ＇as well as on the former hypotheses＇； be
many in number on account of the fact that the ingredients may be
combined with one another in a multitude of ratios； some will be based
on determinate numerical ratios； while others again will have as their
basis a relation of quantitative excess or defect not expressible in
integers。 And all else that was said in reference to the colours；
considered as juxtaposed or superposed； may be said of them likewise
when regarded as mixed in the way just described。
Why colours； as well as savours and sounds； consist of species
determinate ＇in themselves＇ and not infinite ＇in number＇ is a question
which we shall discuss hereafter。
4
We have now explained what colour is； and the reason why there are
many colours； while before； in our work On the Soul； we explained
the nature of sound and voice。 We have next to speak of Odour and
Savour； both of which are almost the same physical affection； although
they each have their being in different things。 Savours； as a class；
display their nature more clearly to us than Odours； the cause of
which is that the olfactory sense of man is inferior in acuteness to
that of the lower animals； and is； when compared with our other
senses； the least perfect of Man's sense of Touch； on the contrary；
excels that of all other animals in fineness； and Taste is a
modification of Touch。
Now the natural substance water per se tends to be tasteless。 But
＇since without water tasting is impossible＇ either （a） we must suppose
that water contains in itself ＇uniformly diffused through it＇ the
various kinds of savour； already formed； though in amounts so small as
to be imperceptible； which is the doctrine of Empedocles； or （b） the
water must be a sort of matter； qualified； as it were； to produce
germs of savours of all kinds； so that all kinds of savour are
generated from the water； though different kinds from its different
parts； or else （c） the water is in itself quite undifferentiated in
respect of savour ＇whether developed or undeveloped＇； but some
agent； such for example as one might conceive Heat or the Sun to be；
is the efficient cause of savour。
（a） Of these three hypotheses； the falsity of that held by
Empedocles is only too evident。 For we see that when pericarpal fruits
are plucked ＇from the tree＇ and exposed in the sun； or subjected to
the action of fire； their sapid juices are changed by the heat；
which shows that their qualities are not due to their drawing anything
from the water in the ground； but to a change which they undergo
within the pericarp itself； and we see； moreover； that these juices；
when extracted and allowed to lie； instead of sweet become by lapse of
time harsh or bitter； or acquire savours of any and every sort； and
that； again； by the process of boiling or fermentation they are made
to assume almost all kinds of new savours。
（b） It is likewise impossible that water should be a material
qualified to generate all kinds of Savour germs ＇so that different
savours should arise out of different parts of the water＇； for we
see different kinds of taste generated from the same water； having
it as their nutriment。
（C） It remains； therefore； to suppose that the water is changed by
passively receiving some affection from an external agent。 Now； it
is manifest that water does not contract the quality of sapidity
from the agency of Heat alone。 For water is of all liquids the
thinnest； thinner even than oil itself； though oil； owing to its
viscosity； is more ductile than water； the latter being uncohesive
in its particles； whence water is more difficult than oil to hold in
the hand without spilling。 But since perfectly pure water does not；
when subjected to the action of Heat； show any tendency to acquire
consistency； we must infer that some other agency than heat is the
cause of sapidity。 For all savours ＇i。e。 sapid liquors＇ exhibit a
comparative consistency。 Heat is； however； a coagent in the matter。
Now the sapid juices found in pericarpal fruits evidently exist also
in the earth。 Hence many of the old natural philosophers assert that
water has qualities like those of the earth through which it flows；
a fact especially manifest in the case of saline springs； for salt
is a form of earth。 Hence also when liquids are filtered through
ashes； a bitter substance； the taste they yield is bitter。 There are
many wells； too； of which some are bitter； others acid； while others
exhibit other tastes of all kinds。
As was to be anticipated； therefore； it is in the vegetable
kingdom that tastes occur in richest variety。 For； like all things
else； the Moist； by nature's law； is affected only by its contrary；
and this contrary is the Dry。 Thus we see why the Moist is affected by
Fire； which as a natural substance； is dry。 Heat is； however； the
essential property of Fire； as Dryness is of Earth； according to
what has been said in our treatise on the elements。 Fire and Earth；
therefore； taken absolutely as such； have no natural power to
affect； or be affected by； one another； nor have any other pair of
substances。 Any two things can affect； or be affected by； one
another only so far as contrariety to the other resides in either of
them。
As； therefore； persons washing Colours or Savours in a liquid
cause the water in which they wash to acquire such a quality ＇as
that of the colour or savour＇； so nature； too； by washing the Dry
and Earthy in the Moist； and by filtering the latter； that is；
moving it on by the agency of heat through the dry and earthy； imparts
to it a certain quality。 This affection； wrought by the aforesaid
Dry in the Moist； capable of transforming the sense of Taste from
potentiality to actuality； is Savour。 Savour brings into actual
exercise the perceptive faculty which pre…existed only in potency。 The
activity of sense…perception in general is analogous； not to the
process of acquiring knowledge； but to that of exercising knowledge
already acquired。
That Savours； either as a quality or as the privation of a